The iWearMonitor software is another component that monitors what games you are running and enables the head tracking driver as needed. The iWearMonitor currently only supports a handful of titles, although the ones supported are popular: World of Warcraft, Second Life, Half-Life 2 Deathmatch, Unreal Tournament 2004, Quake 4, Microsoft Flight Simulator, Lock On and IL2 Sturmovik.
Yep you can get a VR920 (includes head tracking) for 400$ or a AV920 (without headtracking) for 350$....
Read on here
http://www.tomsgames.com/us/2008/02/12/vuzix_review/