Kaisei
Your watch tracked the night. Kaisei reads it when you wake.
Kaisei is a private, on-device recovery and readiness app for Apple Watch owners. Every morning it reads the heart-rate variability, resting heart rate, and sleep your watch already recorded overnight and turns them into one recovery score from 0 to 100 — measured against your own baseline — then does the part most apps skip: it tells you what to do with it. Push, hold, or rest. Your biometrics never leave your phone. No account, no cloud, nothing to log into. The gauge is the kanji 回 — regeneration — a squared ring that glows from ash-grey when you're depleted to vermilion when you're primed, and reignites each morning at today's score.
Six systems behind your morning score
Recovery, Every Morning
One score from 0 to 100, read against your own 60-day baseline — last night's HRV, resting heart rate, and how fully your heart settled overnight. Computed once and fixed for the day, so it never drifts while you check it.
Push, Hold, or Rest
The part most apps skip: a verdict, not just a number. The factor that moved your morning sits right under the ring — "HRV 14% under your baseline" — with an exertion target sized to how recovered you are.
Sleep, Beyond Hours
Deep, REM, efficiency, timing consistency, and 14-day sleep debt — weighed against how much sleep your body actually needed last night, not a flat eight-hour rule. Degrades gracefully when stage data is missing.
Vitals, Your Own Baseline
HRV, resting heart rate, blood oxygen, respiratory rate, and wrist temperature — each shown against your personal normal range, never a chart of strangers. Awareness, framed as personal insight and never as diagnosis.
Private & On-Device
Your biometrics never leave your phone. No account, no cloud, nothing to log into — everything is computed and stored locally. Delete the app and it's gone. Privacy is the architecture, not a setting.
A Real Score on Day One
Been wearing your watch? Kaisei reads your Apple Health history and gives you a real score in your first session — no month-long calibration wait. A thin baseline lands near 50 with honest "calibrating" confidence.
Ready to start?
Get Kaisei for iPhone + Apple Watch