Methods that have been studied, with their real evidence grade shown — including the ones the research does not support.
Focus Crab turns a plan into a session you actually start. You say what is in your way; it offers a small number of methods that match, each carrying its own grade for how well it is evidenced. Nothing is dressed up as science that isn't.
On your device, and — if you leave sync on — in your own iCloud. There is no account to create and no server of ours for it to reach. The privacy policy says this precisely.