Android will remind you how much time you've spent in the current app.

In one of the latest updates to the Digital Wellbeing app, there's been a hidden buildup of a new feature called Screen Time Reminders. When activated, you'll receive a 'gentle reminders' on top if you spending a long time in an app. (from the screen: "Used for 15m")

The reminders come with a certain period, and the list of apps in which they appear will be editable in the Digital Wellbeing settings.

@Assembledebug (via Android Authority) was first to discover the development of this feature in Digital wellbeing app. But, I was also able to demonstrate it working in Android 15 QPR2 Beta 1. So there is a possibility that this feature may also require a system update (or may not).

UPD.: looks like it's already available for some even on Android 15 stable and older

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