If we can get some spare time and pocket change, a friend of mine and me will try to make something that might be better than both (actually, i'll buy the materials and he'll do the soldering and porting the position calculating code form open source projects
).
We are thinking of using a solid-state 6DOF sensor circuit that doesn't need any kind of light going back and forth and will only require a single USB cable to power it (or batteries and no cables at all). There are sensors like these available from many electronics shops online, they are small and have no moving parts at all. If it can be made small enough to clip on a headset it will be awesome.
These things are used to build radio controlled aircraft with autopilots, so i guess it's precise enough for what we want. Best of all, it will not be susceptible to light at all and you won't need to worry about matching a camera's field of view with your head position so that the LEDs remain visible. There will be no camera and no leds, just a small box containing a circuit board clipped to your headphones.