A 3 point headtracking device to be used with FreeTrack ( http://www.free-track.net/english/ ).
EDIT: Use FreeTrackNoIR, it's the successor of FreeTrack
...Zeig mehr (even supports headtracking without an IR device!):
http://facetracknoir.sourceforge.net/home/default.htm
Includes a battery compartment and a opening for a switch.
Designed to be put on top of a headphone.
If you have a Logitech G930 you can use my clip for the G930 to attach the device to your headphone:
http://www.thingiverse.com/thing:47124 (use one with center guides). Or just use velcro tape, or design your own clip :-)
Additional Parts:
-2x M3 screws (10-15mm)
-4x M3 hex nut
-3xLEDs, some electronics, 2x AAA batteries
Credits:
The battery holder is based on this thing: http://www.thingiverse.com/thing:5079
Thanks obijuan!