Jay Honeck wrote:
you can check out the one I have here

http://www.naturalpoint.com/trackir/


Very cool. Of course, the cheaper version is "out of stock"...


Forget the cheap version, get the full "6 degrees of freedom" - you
really won't regret it. I found that the head movement was completely
intuitive, and much less of a problem that I thought it might be. With
the 6DOF you can also lean forward to get a better look at the
instrument panel, or lean sideways and look downwards out of the side
windows for sightseeing. Of course if you lean too far your head will be
out of the cockpit, but its a lot less windy in the sim. :-)