What about it?
There are VR systems that use IR, which would render head movement relative to attitude of the machine. What's keeping them from doing so?
Plus, the headset in the video probably just renders the images in 3D, he doesn't seem to be moving his head.
Video of the machine at a Navy Recruitment booth:
http://www.youtube.com/watch?v=KvzkgEpbyecLooks like fun... I'd love one someday...

Seems like they are using the Vuzix VR headset in this video, I think that uses accelerometers. I assume the motion simulator would probably mess with it a bit.