Four documents. Between them they describe every interval the system uses, everything it can read, and everything it refuses to do.
The daily check-in, the six rungs of the escalation ladder, guardians and rank order, and how travel holds work.
What is encrypted client-side, what we can read, what happens if you lose your passphrase, and the failure modes we design against.
Live status of every subsystem, incident history, and how we count uptime against escalation correctness rather than server reachability.
Every release, and the changes we have declined to ship.
There is no public API. Check-ins are deliberately limited to the app, a paired watch and email, because an API key that can confirm you are alive is an API key that can confirm it on a day you aren't.