I used to play with stopwatches a lot.
The game method is simple and nothing to explain. The person who closes the clock at the closest time wins the game.

For example, if you set the time to 30 seconds, start with the stopwatch (recording timer) and press the button in front of you when you think it is 30 seconds without looking at the clock.
And check the time, the closest person in 30 seconds wins the game.

Each group made it possible to have only one tablet.
You can do it alone, or you can do it at the same time.
If you use it well in class, you can use it to refresh your surroundings during tedious hours, to pick a presenter, or simply to play a game.