Qt Drumkit is one of the Nokia Developer projects that are available for testing at Nokia Developer website. I've already posted a YouTube presentation of the apps capabilities. This application is truly remarkable as it's one of few official Nokia Developer projects we've witnessed in a long time. The application allows you to play finger drums on your Nokia N9, it uses multitouch and offers two views: realistic drumset and convenient black pads for touch-drumming. You can also record your beats and play them back later. It is also possible to play on top of your last recording.
This application is fun as hell, and will definitely keep your attention deficit nephews busy for a while, so it's worth to give it a try. The app isn't afficially available from the Nokia Store at the moment, so you will need to download the package, and install it following these instructions.