Well here's an innovative homebrew for your DS. It's called the DSMouse and, as the name implies, it allows your DS to become your mouse.

Dankredues has written a PC application that converts signals from your DS to your mouse, allowing you to control the pointer on your computer screen with your DS rather than with your usual mouse. Granted, the applications of DSMouse are limited, but it makes for an interesting prank scenario at the very least.

Three things to note, before you try the application. First off, DSMouse v0.3 A uses ports 111 and 112 on your computer, so be sure to keep them free. Second, according to Dankredues, "The windows server has to be terminated by the taskmanager." Lastly, the app doesn't have a readme, so you'll have to be careful in using the application.

That being said, if you have the technical know-how, give it a try, and see what happens. Enjoy!