DetoxDroid

Most digital detox apps are opt-in. You start a timer and then try not to break it. DetoxDroid works the other way round: a calmer phone is the default state, and you take deliberate pauses out of it.

In practice that means the screen stays mostly grayscale with exceptions for the apps where colour actually carries information, Do Not Disturb is on unless you say otherwise, chosen apps are disabled during detox hours, and a long scrolling session gets interrupted by a prompt. A commitment password can lock the settings so that the version of you at 1am cannot undo the decisions of the version at 9am.

Under the hood the whole app hangs off one Android accessibility service, and every feature plugs into it rather than being built separately. A new one is a small addition instead of an operation on everything else, which is roughly what decides whether a side project is still alive two years later.

It is free software, around 500 stars on GitHub, and it needs privileged permissions that Google Play will not grant, so it installs over ADB with a script instead of from the store. That cost it a lot of users and kept the feature set honest.