Umbro for iPhone and iPad
The same engine this site runs on, compiled to Swift and running on the device — so it works with no signal at all, in the middle of an ocean, which is where a good many eclipses are.
On the Lock Screen
A Live Activity counts down to first contact, then to each contact after it, and its icon changes as the eclipse moves from partial to totality and back. Home Screen widgets carry the countdown, the coverage and the sky at maximum.
A camera for totality
Exposure locked and stepped through a bracket suited to each phase, re-metering as the Sun climbs or sinks, and an HDR corona stack merged from the totality frames. A thin crescent and a full corona are not metered the same way.
Told when it is safe
The app says plainly when the Sun cannot be looked at without a filter and — during totality only — when it can, from the contact times computed for your exact position rather than from a rule of thumb.
Watching from a ship
Choose a position out in open water and Umbro offers a vessel mode that accounts for drift and for the roll of a deck when it works out contact times and camera settings.
Everything on this website stays free and needs no app. The app adds what a web page cannot do: the Lock Screen, the widgets, the notifications and the camera.