Basically, the idea is quite simple.
Provide a simple brick breaker or whatever then try to change score or any parameters.
Then submit it,.
The android app, should store the whole parameters into a file.
Android Hacks are a growing vector in the matter of Hack skills , google is hiring to find some 0Day are any other program flaw.
Yeah, this is a growing trend in my opinion… I’m getting a lot of messages asking for help on this subject (even though most of the times it is not really complicated)
There is a lot of (easy to find) documentation online if you want and, as @dloser said, you can find this type of challenges around.
Actually in some ways it’s not so different from the old java challenges on some sites.
I think an android challenge will need to be more deeply android related to be interesting.
Maybe bypass pin security or use camera/voice to spy and then discover things about the room around you.
Find password from other apps by breaking the sandbox etc