This dude rocks.. I've got a wii so i decided to give it a try. (I don't have a projector so i tried with a lcd display) It took me maybe 15 mins to build a pen. (i just took the ir led out of a remote control i don't need). For those who wanna try: Find a remote control you don't need, remove the ir led (you need a soldering iron for this), solder wires to the ends of the leds contacts. Then mount the led onto the tip of an "emptied" ballpoint pen. The wires should go through the pen. If you haven't got a switch at hand just tape a AAA-sized battery onto the side of the pen and solder one cable to the plus pole and tape the other wire to the side of the battery so that you can bend it and touch the minus pole with the wire. If you did it properly the wire will go back to its former position when you lift your finger and opens the circuit again, so that only when you push the wire down to the minus pole the circuit closes and the led emitts ir light. Don't be confused if you don't actually see any light. IR-light is invisible to the human eye, but not for the camera as you can see in the vid. Since a LED is as the name says a light emmitting DIODE it only works with the right poles so before you solder any wire to the battery, check that it is actually working (with the software provided on his webpage).
The software works flawlessly and it is really accurate. The tracking speed could be a bit better maybe but i don't know if this is limited by the hardware of the wiimote or the software. Anyhow nice work!