How To Build Your Own IR Head Tracker
From: Maximum PC - 12/2010 - page 62

With all the recent hubbub about Microsoft's Kinect and Sony's PlayStation
Move, you’d be excused for thinking that motion control is some new
phenomenon. In reality, it's a technology that's been around on the PC for
years. Head tracking allows you to control your PC with your head. Mostly
used in sim games, head tracking lets you move and tilt your head to control
where your character looks. There are, of course, some excellent commercial
head-tracking systems available, but it’s possible (thanks to free software
called FreeTrack) to build your own head tracker with just a webcam and a few
dollars worth of electrical supplies. 

Read the entire article at:
http://www.maximumpc.com/article/how-tos/how_build_your_own_ir_head_tracker

Links:
FreeTrack
http://www.free-track.net/english/freetrack/telechargement.php

Kinect
http://www.xbox.com/en-US/kinect/

Move:
http://us.playstation.com/ps3/playstation-move/