Pokémon Sleep is a Pokémon game for Android devices developed by The Pokémon Company. The most interesting thing about Pokémon Sleep is that, to play it, you have to be sleeping. Through sensors such as your smartphone's accelerometer, Pokémon Sleep is able to analyze your sleep patterns. In order for it to detect them, you'll need to place your smartphone or tablet on your pillow or bed.
If you want even more accurate data, you can purchase Pokémon Go Plus+, which is valid for both Pokémon Sleep and Pokémon Go. To use it, simply tap the central button when you go to bed and again when you wake up.
After analyzing your sleep, Pokémon Sleep breaks it into three different phases: light sleep, medium sleep, and deep sleep. In each phase, you'll attract different types of Pokémon to your base, which is a Snorlax. As you progress through the game, you'll unlock more sleep modes to add to your DormiDex.
The creators of this game wanted to encourage healthy sleep habits for kids, as well as motivate them to wake up in the morning, since they'll be excited to see the results. The more you sleep, the higher the score you'll get in Pokémon Sleep, and the more Pokémon will appear.