“FreeTrack is a free optical motion tracking application for Microsoft Windows, released under the GNU General Public License. …
Head motions are tracked with six degrees of freedom (6DOF), specifically; yaw, pitch, roll, left/right, up/down and forward/back. …”
This is a really cool application that I use with Flight Simulator. It’s exactly like the commercial product Track-IR but it’s totally free and open source. All you have to do is build your cap the way you want. you have all the information on how to do it on the website, a great community to help you on the forum (and I think some people can build one for you if you ask 
)
You really should take a look at it 
More videos : http://www.free-track.net/english/multimedia/video.php
Compatible Games : http://www.free-track.net/english/freetrack/liste-titres-compatibles.php
The Website : http://www.free-track.net/english/
