Training and nutrition tracking with an AI coach you can talk to between sets: real-time voice, three interchangeable model providers, and billing that survives retries.
- Role
- Architect and sole engineer
- Year
- 2025 – 2026
- Status
- Beta
- Links
- vitalitylabs.app
VitalityLabs is a health platform with an AI coach at the center of it: a Next.js 14 web app, an Express/MongoDB backend and an Expo mobile app, with Anthropic, Gemini and Grok wired in as real, interchangeable providers. I rebuilt the AI engine as a v2 with native function calling and streaming and migrated off v1 in a documented cutover (ADR-13).
The voice deck — "Bridge" — does voice activity detection in wasm, acoustic echo cancellation, barge-in, continuous mode, wake word and speech-speed control, so the assistant can be talked over instead of waited out.
Running models for real users means knowing what they cost, so it also carries a token economy (wallet, ledger, per-provider BPE token counting, a cost matrix and metering middleware) and dual-rail billing on Stripe and PayPal over direct HTTP with webhook signature verification, idempotency and promo codes. Plus Withings and Health Connect body-data import, an admin console with AI telemetry and GeoIP, and a Vitest + Playwright suite including a visual-regression screenshot harness.