Cross-platform health app with 3× user engagement.
A health-tech startup needed a companion app that synced with wearable devices, tracked biometric data offline, and kept users engaged long-term. We built a React Native app with BLE integration that tripled daily active usage.
The short version.
A health-tech startup had built wearable hardware for biometric monitoring but their companion app was a basic data viewer with 15% 30-day retention. Users would check it once after a workout and forget about it. The hardware was excellent but the software experience was killing their business.
We rebuilt the companion app from scratch as part of our mobile app development engagement, with BLE wearable integration, real-time biometric visualization, personalized insights, and gamification. Daily active usage tripled, 30-day retention jumped from 15% to 60%, and the app became a key selling point for the hardware.
Great hardware, forgettable software.
The wearable device collected excellent data (heart rate, SpO2, sleep quality, activity levels) but the app didn’t do anything meaningful with it:
- 15% 30-day retention: users tried the app once or twice and stopped opening it; data just sat there
- No offline sync: BLE connection required the app to be open and in foreground; workout data was frequently lost
- Raw data dumps: app showed numbers without context; users didn’t know what their heart rate variability meant
- Platform inconsistency: iOS and Android apps were built separately with different features and bugs (the classic native vs hybrid problem)
- No engagement hooks: no streaks, no goals, no social features, no notifications; nothing to bring users back
Reviews on both stores averaged 2.8 stars, with complaints about reliability and “what’s the point” being the most common themes.
Data-driven engagement with reliable BLE sync.
We rebuilt the entire app with two priorities: rock-solid data collection and meaningful user engagement. Every feature was designed to turn raw biometric data into actionable insights:
- Background BLE sync: data syncs reliably even when the app is backgrounded; no more lost workouts or sleep data
- Personalized insights: algorithms analyze trends and surface meaningful observations (“Your recovery time improved 15% this week”)
- Goal system with streaks: daily and weekly goals with streak tracking; push notifications for motivation at optimal times
- Rich visualizations: animated charts showing heart rate zones, sleep cycles, activity patterns, and long-term trends
- HealthKit / Google Fit: bidirectional sync with platform health APIs; users see all health data in one place
- Offline-first architecture: all data stored locally; cloud sync when connected; works perfectly on airplane mode
React Native with native BLE bridge.
The app uses React Native for the UI with a native Kotlin/Swift bridge for BLE communication and background processing. All biometric data is stored locally in SQLite and synced to the cloud when connectivity is available.
Offline-first | zero data loss, background BLE sync
The BLE communication layer handles 12 different wearable devices through a unified abstraction. Each device’s protocol quirks are handled in the native bridge, so the React Native layer receives normalized biometric data regardless of hardware.
“The old app was our biggest weakness. Now it’s our biggest selling point. Users actually look forward to checking their insights, and our hardware return rate dropped because people finally understand the value of the data.”
CEO, Health-tech startup
Building an app
that connects to hardware?
We specialize in BLE integration and offline-first architectures for health and IoT devices.