The Sound activity from Childsplay could be ported with extra enhancements that it plays not just one soundfile, but multiple soundfiles to increase difficulty.
So the first level would just play 1 soundfile and remove the icon when clicked correct.
The second level would also play 1 soundfile, but not remove the icon when clicked correct.
Third level would play 2 soundfiles in sequence, and the user has to click them in correct order.
Further levels can increase the number of soundfiles to be remembered.