Headtracker from ZEISS (USB, ready to use any system, mouse-wise) http://www.zeiss.de/cinemizer-oled/de_de/produktinformation.html
but 150,- bugs.. euros?

an own headtracker, based on Arduino + sensors would cost hardware at least 20+20+20 60 Euros an lot of work…

a CARL ZEISS cinemizer costs 650,- bugs, insane, crazy..
http://www.rcmodellbau-online.de/ 560,- euros
and we have no chance to test? ok, order and send back within legal time.
without testing such a device i would hang a Xperia 3 tablet infront of my eyes..
the tablet would be usefull as tablet too.. when you are not playing..
but with a tablet infront, we need exact headtracking… is a 20 bugs air mouse accurate enough?
first test with arduino and
Gyro: Triple Axis Gyro – L3G4200D (BK-L3G4200D)
Accelerometer: MMA7361L 3-Achsen Beschleunigungssensor (IM120712010)
show, that accurate headtracking isnt done with a snip..

for DIY  headtracker we have to leave single sensors behind us.. gyro, accelerometer, magnetometer… there are complete sensors available, doing combining all of them
http://en.wikipedia.org/wiki/Inertial_measurement_unit