For starters, check You Tube for other videos by Johnny Lee, both Wii hacking, and other things he's done. He's a smart guy who is big on finding ways to bring high end technology to the masses.
As far as the head tracker goes, I bought a used Wii controller online for $10 bucks, and spent another $10 at radio shack buying infra red LEDs, batteries and such, and built my own IR pen. The way it works is you pair the Wii to your PC, then you load the software (which is available for free from Johnny Lee's website), and then you simply point the controller at your monitor (or in my case, I actually sent my video output to my 32" HDTV), and when the software executes there's some pick points in the upper and lower right and left of the screen. You put the IR pen tip (the IR LED) on the point and press the button at each point. Once done, the device effectively replaces you mouse. You can move windows, open folders, etc. I opened Photoshop and was able to select various brushes and colors and was painting on the screen.
While it's not 100 percent perfect, the "resolution" is a bit on the low side, it DOES work VERY WELL overall.
Johnny Lee was, due to the whole Wii hacking thing, hired by Microsoft and he worked about 2 1/2 years on the development of the Microsoft Kinect, and, the Kinect is an even cooler device than the whole Wii hack, and there's a ton of cool Kinect hacks out there as well. On top of that, Microsoft has embraced the whole Kinect Hack community. While the Kinect was developed for the XBox, people quickly were hacking it on a PC, so Microsoft actually did something I agree with for once, embraced the PC hacking work, and has since released an SDK
Last I heard, Google hired Johnny Lee recently, and, although I don't know exactly what he's doing for them, he's probably the lead on the Google Goggles project.
