Idk, my impression always was and is that Android app development is complex, especially when you got Java in the mix....maybe now it's easier when Kotlin is around.

Your idea is very good and you can even monetize your app by selling ad space when users choose "boredom" then you can recommend them sponsored apps and games.

This idea would be also interesting on PC, when users lock their screens and then come back to do something. Maybe it can even be part of some diary/note taking app where when you unlock your screen note window pops up and asks you "What are you planning to do now?".