Fitnis
A fitness coaching app where the entire experience is just a conversation with an AI coach. No forms, no tabs, no menus. You just chat.
2024 — Present
Description
Fitnis throws out the typical fitness app playbook. Instead of a million screens for logging workouts, browsing exercises, and checking stats, the whole thing is just one chat interface. You talk to an AI coach called Fitniz, and it handles everything.
Want to start a workout? Just say so. Did 8 reps at 100kg? Tell it. Want to see how your bench press has progressed over the last month? Ask it, and it'll pull up a chart right there in the chat. You can even photograph a handwritten workout sheet and the AI will read it and log everything for you.
The coach remembers your history, suggests progressions based on your last session, and keeps things on track. It feels less like using an app and more like texting a personal trainer who's weirdly good at data analysis.
What I did
- Designed and built the entire product end to end, from concept through to a working app
- Created the chat-first UX, including all the rich UI elements like interactive choice buttons, workout summary cards, and progress charts
- Built the frontend in Expo React Native for iOS and Android
- Built the backend in Hono (TypeScript) with PostgreSQL
- Integrated multiple AI providers (Anthropic, OpenAI, Google, DeepSeek) with streaming responses and tool use
- Designed the workout tracking data model and the AI coach's persona and prompt system
- Built the photo import feature with on-device compression and AI vision analysis
