Here is an application to turn your DS into a motion sensing USB gamepad. You’ll need a DS Motion Card or MK6-motion or R6 gold for the motion sensing, and an MK5 (or clone) GBA slot USB linker. Plug all the cards in, plug the USB cable into your computer, and run the application. Presto – a motion sensing game controller.

http://forum.gbadev.org/viewtopic.php?t=13753