Japanese modders have made their own Kurukuru kart, a recreational vehicle you can control directly with a hacked Wiimote.
Looks like a lot of fun if you have a lot of time to kill. 🙂
There isn’t a whole lot of information available on this besides the video captions, but it appears to be using the WiiFlash Flash API for Wiimote input and Gainer for motor control output. WiiFlash looks like a particularly interesting tool for Flash developers. You can run the WiiFlash server component on a Windows or OS X desktop and then use a simple Actionscript API to access the Wiimote within your application.