Health data

Everything a device or a scale says about me — weight, body composition, resting heart rate, sleep stages, stress, steps. The numeric side of Body.

Nothing here yet because the device isn't bought. The current plan is cheap, Android-native, zero subscription:

• Xiaomi Smart Band 9 for sleep, heart rate, stress, steps (~$40).
• Xiaomi Mi Body Composition Scale 2 for weight, body fat, muscle mass, water (~$30).
• Mi Fitness (the official Xiaomi Android app) writes both into Android Health Connect.
• Health Data Export (Android app, ~$5 one-time) reads Health Connect and POSTs daily JSON to this site's /api/ingest/health endpoint.
• The endpoint writes src/data/metrics.ts and commits it. Git becomes the time-series database. The page you're reading right now renders from that file.

Absolute sensor accuracy isn't the goal — trends are. A cheap tracker that gives me the same number to within the same error-bar every day tells me everything I need to know about where my sleep, weight, and recovery are going.

The architecture is intentional: the wearable is a swappable component. Android Health Connect sits in the middle. Swap the band or the scale next year without rewriting the pipeline.

What this page will render when wired

• Current weight + 7-day moving average
• Body fat % trend (30-day)
• Sleep duration sparkline (last 30 nights)
• Resting heart rate drift
• Stress / recovery score (Mi Fitness derives this from HRV-adjacent signals)

No dashboards of 40 metrics. Just the handful that move.