Ten minutes, two machines, and your life never leaves your own computer. Here's the whole thing, simply.
Lifeline is an app on your phone (it appears there as Loose Ends) and an engine on your Mac. The engine is the part that reads your mail, messages, and calendar — and it runs on a computer you own, because the whole point is that nobody else ever holds your life. The phone app is just the window into it.
So you need: an iPhone, a Mac that stays switched on (an old laptop in a drawer works fine), and about ten minutes.
One command in Terminal installs it. When it finishes, a setup page opens in your browser and takes over — you won't touch the Terminal again.
Lifeline is in active development. The one-command installer ships with the first public release — if you're reading this before then, the engine is built from source.
Four things, and the page walks you through each one, checking its own work as it goes:
The app fills with the open loops found in your own mail and messages — each one worked quietly in the background. Your phone buzzes for exactly three things: an answer to something you added yourself, a deadline inside a day, or a drafted message ready to send. Everything else waits politely in the app.
Nowhere. The engine keeps everything in a database on your Mac. There is no Lifeline cloud, and notifications are delivered by a relay that can't read them — it only ever carries a knock, and your phone fetches the words from your own machine. The details are in the privacy policy.