Check out this video for some awesome, cheap, easy DIY wiimote hacking fun. All you really need is a wiimote, a bluetooth interface for your PC and an infrared LED. You can obtain the LED from an old TV Remote if you don't want to go out and buy one, this is what I did so I can testify that it will work. This works really well as you can see from the video, however, placement of your wiimote is really important as it's sensitive to obstruction and distance. Regardless of the limitations this is truly awesome! It took me maybe an hour to make a shoddy light pen, download his software and install his recommended bluetooth driver.