"VideoGamesHero brings you homebrew action at it's best - offering lasting fun and challenging action with over 65 Songs, 5 Game modes, Motion Card and Guitar Grip support, there is something for everyone!" Homebrew Harmonix-style rhythm action game for the ds. Awesome.

"glitchDS is a FREE homebrew Cellular Automaton music sequencer for the Nintendo DS. It’s perfect for creating IDM and Glitch style loops." Should only work with R4, but seems to work with several carts.