The Challenge
A fitness startup in Berlin needed a mobile app that could differentiate from crowded fitness apps by using the phone camera for real-time rep counting — plus nutrition tracking, a trainer marketplace, and Stripe subscription billing.
Our Solution
React Native for iOS + Android. TensorFlow Lite for on-device pose estimation and rep counting. Node.js backend with Firebase for real-time data. Stripe for subscription billing with free trial. Custom trainer dashboard in Next.js.
Architecture Highlights
On-device AI. The rep counter runs entirely on the user's phone — no cloud calls needed. TensorFlow Lite model trained on 10K+ exercise videos for 93% accuracy across 15 exercises.
Trainer marketplace. Trainers create profiles, set availability, and receive bookings. Revenue share handled automatically via Stripe Connect.
Results
12K+ downloads in the first 30 days. 4.7★ average rating. 68% D30 retention. $18 average revenue per user. Featured in "New Apps We Love" on the German App Store.