--- title: "Mobile App Development: Ramón Chancay" description: "Production iOS and Android apps with React Native, Expo, Swift and Kotlin." author: Ramón Chancay lang: en canonical: https://www.ramonchancay.me/mobile --- # Mobile App Development: Ramón Chancay Production iOS and Android apps with React Native, Expo, Swift and Kotlin. ## Shipped apps ### pet-meet A community app for finding lost pets: live map, location-based alerts and smart QR collars that work without installing anything. - Platforms: iOS · Android - Challenge: When a pet goes missing, every minute counts. Reporting had to take seconds, alerts had to reach only people near the location, and the QR collars had to show contact info to anyone who scanned them, with no account or app install required. - Solution: A React Native/Expo app for iOS and Android with a live map of reports and geolocated push notifications. Each collar carries a QR that opens a public web page with a deep link into the app. Behind it: a Fastify backend, a Next.js admin panel for collar inventory, and a public Astro site, all in one monorepo. - Architecture: Turborepo monorepo: React Native/Expo app, Fastify backend on Supabase, Next.js admin panel and a public Astro site with per-pet deep-link pages. Twilio for verification and AWS S3 for media. - Outcome: Live on the App Store and Google Play, with a physical QR-collar ecosystem operating on top of the platform. - Features: Live map (Lost-and-found pet reports on a real-time map, with photo, description and last known location.); Location-based alerts (Push notifications that reach only users near the report location: signal, not noise.); Smart QR collars (Scanning shows the owner’s contact info on a public web page: works for anyone, no account needed.); Friends network (A trusted circle of contacts who get your pets’ alerts first.); Operations panel (Next.js admin for collar inventory, distribution centers and PDF shipping manifests.) - Case study: https://www.ramonchancay.me/mobile/pet-meet ### intervatar An AI interview coach: ask a question out loud and the app answers from your resume, job description and STAR stories, plus a copilot for the real interview. - Platforms: iOS · Android - Challenge: Job seekers walk into interviews with the information in their head but not the words. Their resume, the job description and their stories had to become answers ready to say out loud, in seconds, and the app had to stay with them during the real interview: on screen, without the glow giving away that they are reading. - Solution: A React Native/Expo app for iOS and Android on top of a Python backend. Speech is transcribed with Deepgram and answers are generated through model routing via OpenRouter, always grounded in the context the user loaded. The interface is dark-only and OLED-first (true black and gold), designed to be used while nervous and under pressure, with a Pro subscription on in-app purchases verified server-side. - Architecture: Expo 53 and React Native with React Navigation and Reanimated, on a Python REST API deployed to Railway. Deepgram for speech-to-text, OpenRouter for model routing, in-app purchases with expo-iap verified against the App Store and Google Play from the server, and full i18n (English and Spanish) with react-i18next and device language detection. - Outcome: In beta testing (TestFlight and a closed Google Play track) while the public launch is prepared, with the whole product working end to end: onboarding, digital twin, voice practice and subscription. - Features: Voice-first Practice Coach (Tap the mic, say the question, and the answer appears in place, with why that answer works and the key phrases to hit.); Answers that fit the moment (The same story as a 30s or 60s reply, an executive or technical version, or in STAR format, depending on the interview.); Your digital twin (Resume, job description and STAR stories as the base of every answer: nothing invented outside your own material.); Scored mock interviews (Mock interviews and voice practice with personalized questions, coaching feedback and a performance review.); Zero-Glow Live CoPilot (A true-black HUD for the real interview, lighting the fewest pixels possible so the screen does not reflect on your face.); 3 free minutes of Pro (Instead of a multi-day trial, each account gets 3 minutes of the full Pro set: the good part, with no card required.) - Case study: https://www.ramonchancay.me/mobile/intervatar ### otv-go Oromar TV’s streaming platform: live TV, on-demand content, vertical shorts and news, on iOS, Android and web. - Platforms: iOS · Android · Web - Challenge: Bring a regional TV channel to mobile: stable live TV, an on-demand catalog, a 9:16 vertical shorts format ("rapinovelas") and the news portal, with subscriptions and notifications, and with video costs under control. - Solution: A mobile app built with Expo and a Next.js web app sharing the same content backend. Video is served through Bunny CDN to keep latency and costs down, authentication runs on Clerk, notifications on OneSignal, subscriptions on RevenueCat, and news is managed in WordPress as a headless CMS. - Architecture: Expo (mobile) and Next.js (web) on a common content backend: Bunny CDN for video delivery, Clerk for identity, OneSignal for push, RevenueCat for subscriptions and WordPress as the news CMS. - Outcome: Live on the App Store and Google Play as the channel’s official app, serving live and on-demand video in production. - Features: Live TV (The channel’s live signal inside the app, with stable CDN-backed playback.); On-demand content (A catalog of shows and episodes available on demand.); Rapinovelas (9:16 shorts) (A vertical short-video format built for quick, feed-style consumption.); News portal (The outlet’s news managed in WordPress and served in app and web.); Push & subscriptions (Notification campaigns with OneSignal and monetization with RevenueCat.) - Case study: https://www.ramonchancay.me/mobile/otv-go ### revup A fintech app for content creators and MCNs: music revenue, channel analytics and withdrawals, with banking-grade security. - Platforms: iOS - Challenge: Creators and MCNs needed to see their music revenue and channel performance from their phone and move money. That demands the sensitivity of a financial app: strong authentication, clear data, and a polished experience in multiple languages. - Solution: A React Native/Expo app in TypeScript: analytics dashboards with trend charts, balance and withdrawal management, per-channel performance tracking, biometric authentication (Face ID / fingerprint) and multi-language support with i18next. - Architecture: React Native/Expo with TypeScript, React Query for remote data, Formik for forms, Nativewind for styling and Axios against the financial API. Native biometrics for access. - Outcome: Published on the App Store, in production for creators and MCNs with real financial operations. - Features: Analytics dashboard (Revenue and trends in clear charts, designed to be read in seconds on mobile.); Balance & withdrawals (Available-balance management and the funds-withdrawal flow inside the app.); Channel performance (Tracking for each channel and revenue source.); Biometric authentication (Face ID and fingerprint protecting access to financial information.); Multi-language (Localized interface with i18next for an international user base.) - Case study: https://www.ramonchancay.me/mobile/revup ### arcavida A natural health and wellness platform with an AI chat, remedies library and health journal, on web and mobile. - Platforms: iOS · Android · Web - Challenge: Knowledge about natural remedies lives scattered and without context. The product needed to turn it into trustworthy, personalized guidance: an AI chat that answers grounded in a curated content base (not whatever the model invents) alongside a browsable library and a health journal. - Solution: A mobile app built with Expo and a web app on Express + tRPC + React sharing the same backend. The health chat uses the OpenAI API over the curated herbs-and-remedies base, the journal tracks user progress, and Stripe handles payments. - Architecture: An Express backend with tRPC for an end-to-end typed API, a React web app and an Expo mobile app. MySQL/TiDB with Drizzle ORM as the data layer, OpenAI for the chat and Stripe for payments. - Outcome: A production platform with web and mobile serving the same curated knowledge base. - Features: AI health chat (An OpenAI-powered conversation grounded in the curated remedies base: contextual answers, not generic ones.); Herbs & remedies library (A browsable catalog of natural remedies and herbal medicine.); Health journal (A personal log of symptoms, habits and progress over time.); Personalized guidance (Recommendations adapted to each user’s profile and history.); Stripe payments (Monetization and payment management built into the platform.) - Case study: https://www.ramonchancay.me/mobile/arcavida ### sudapp A fitness rewards app: every workout earns "Drops" redeemable for partner-brand benefits, with rankings, streaks and communities. - Platforms: iOS · Android - Challenge: Workout motivation fades when the only reward is invisible. The product needed to turn exercise into tangible rewards: read real user activity from Apple Health and wearables like Garmin, measure effort honestly (intensity and duration derived from heart rate, without storing more sensitive data than needed) and connect it all to a catalog of local brand benefits per city. - Solution: A React Native/Expo app in TypeScript for iOS and Android. It links with Apple Health and devices like Garmin to track workouts automatically; each session earns "Drops" based on intensity and duration. Points are redeemed in a benefits marketplace filtered by city and category (products, food, services), and the app gamifies consistency with weekly rankings, streaks, challenges and communities. - Architecture: A React Native/Expo app in TypeScript, integrated with Apple Health (HealthKit) and devices like Garmin. Heart rate data is used only to compute workout indicators (intensity and duration) never stored or shared. Device linking/unlinking and coupon redemption happen in-app. - Outcome: Live on the App Store and Google Play in Colombia, with an ecosystem of 110+ partner brands, 40,000+ recorded activities and thousands of redeemed vouchers. - Features: Automatic activity tracking (Workouts and heart rate read from Apple Health and linked wearables like Garmin.); Drops per workout (Each session earns points computed from real effort indicators: intensity and duration.); Benefits marketplace (Coupons and offers from partner brands, filtered by city and category, redeemable in-app.); Gamified Drop Zone (Weekly ranking, streaks and goals that turn consistency into friendly competition.); Communities & challenges (User groups and shared challenges to train together.) - Case study: https://www.ramonchancay.me/mobile/sudapp ### menonita-health A hospital management system with a mobile app: patients, appointments, medical records and insurance, secured with biometric authentication. - Platforms: iOS · Android - Challenge: Digitize a health system’s operations (patients, appointments, medical records and insurance) with the security requirements clinical data demands, and give patients and staff mobile access as protected as the core system. - Solution: A REST API on NestJS + TypeORM + PostgreSQL as the system’s backbone, and an Expo mobile app for user access. Identity runs on AWS Cognito, mobile access is protected with biometric authentication, and Redis speeds up high-frequency operations. - Architecture: REST API with NestJS, TypeORM and PostgreSQL; an Expo mobile app consuming the API; AWS Cognito for identity and sessions; Redis as a cache layer for high-frequency operations. - Outcome: An enterprise system in production, with the mobile app as the secure gateway into the hospital system. - Features: Patient management (Registration, history and follow-up of patients in a single system.); Medical appointments (Scheduling and management connected to the patient’s record.); Medical records (A structured digital clinical history, accessible from mobile.); Insurance (Insurer and coverage management integrated into the care flow.); Biometric authentication (Face ID and fingerprint on top of AWS Cognito protecting sensitive clinical data.) - Case study: https://www.ramonchancay.me/mobile/menonita-health ## Frequently asked questions ### How long have you been building mobile apps? Ramón has been shipping production software since 2012, more than 13 years, and has worked on mobile since 2019: React Native bridge apps at Desarol, then senior full-stack mobile developer at NativApps, and lead React Native developer for a mobile team in Madrid. The apps shown here are the most recent ones, released between 2024 and 2026; the experience behind them is far older than those release dates. ### Do you build apps for both iOS and Android at the same time? Yes. Ramón builds cross-platform apps with React Native and Expo, so one codebase ships to both the App Store and Google Play. Pet-Meet and OromarGo are live on both stores today, and RevUp is on the App Store: real production apps, not prototypes. ### Do you only work with React Native, or also native iOS and Android development? Both. React Native with Expo is the default when sharing one codebase across both stores makes sense, and most of this portfolio shipped that way. When the product calls for it, Ramón also builds fully native: Swift and SwiftUI on iOS and Kotlin with Jetpack Compose on Android, using the platforms’ latest APIs (widgets, Live Activities, App Intents, Material You). And in between, React Native apps with custom native modules in Swift/Kotlin for camera, sensors, third-party SDKs or performance-critical paths. ### How long does it take to build a mobile app, and what does it cost? A focused mobile MVP (the core flows, working on real devices, submitted to the stores) typically ships in 4 to 8 weeks. Cost depends on scope (screens, backend, integrations like payments or push notifications), so pricing is quoted per project after a free 30-minute call to define the use case. You get scope, timeline and a fixed price in writing before anything starts, with no cost if you decide not to go ahead. Larger products like streaming or health platforms take longer and are scoped in phases. ### Do you handle publishing to the App Store and Google Play? Yes, end to end: app signing and builds with Expo EAS, store listings, screenshots, review guidelines, and the back-and-forth with Apple review until the app is approved. Every store-published app in this portfolio went through that process with Ramón driving it. ### Can you integrate AI into a mobile app? Yes. It is one of his specialties. ArcaVida ships an AI health chat built on OpenAI inside a platform with an Expo mobile app, answering grounded in a curated remedies base. He wires the model, the backend and the mobile UI end to end. ### What happens after launch? Apps need maintenance: OS updates, store policy changes, and new features. With Expo, many fixes ship instantly as over-the-air updates without waiting for store review. Ramón offers ongoing support: monitoring, push notification campaigns, analytics, and iterating on what users actually do. ### Do I also need a backend or a web version? Can you build those too? Most real apps need a backend (accounts, data, notifications) and often an admin panel or website. Ramón works full-stack: Pet-Meet, for example, is a React Native app plus a Fastify backend, a Next.js admin panel and an Astro public site, all in one monorepo: one person, no coordination overhead between separate contractors. ### Who owns the code and the App Store and Google Play accounts? You do. The repository, the code and the store accounts are published under your name and stay yours, so you are never locked to one developer. Ramón can keep maintaining the app afterwards, but that is a choice, not a dependency, and he signs an NDA when the project needs one.