OwnTime

OwnTime borrows the shape of a chess clock. You define a few priorities, give each one a daily time budget, and only one clock runs at a time, so starting a task pauses whatever was running before. An alarm goes off when a budget is spent, and everything resets at midnight. It runs on iPhone and Apple Watch, which stay in sync when paired, and each device also works on its own. There is no account and no server behind it.