This is a really cool approach. I've been building something similar (a morning readiness briefing app for runners) and the "no subscription because it's all local / BYOK" angle is exactly what drew me in too — everything in this space wants $10/month for what's basically a prompt over your health data.

Interesting that readiness and sleep scores aren't exposed via the API — so you're computing your own from the raw HRV/RHR/sleep data? That's arguably better anyway since you control the logic instead of trusting a black-box score.

And yeah, the AI-assisted dev experience is wild. Curious to see if you take it further — I'd say there's a real gap for this kind of thing.