Has anyone else given this a shot? I got it working in AC with my old Galaxy Nexus. It's not accurate enough for aiming but still pretty cool taste of head tracking for those of us too poor for TrackIR, and too lazy to mess around with modding a webcam.
https://github.com/opentrack/opentrack/wiki/Smartphone-Headtracking
The only truly annoying thing I've come across is that you can't re-center the axis position inside of AC while in fullscreen mode.
https://github.com/opentrack/opentrack/wiki/Smartphone-Headtracking
The only truly annoying thing I've come across is that you can't re-center the axis position inside of AC while in fullscreen mode.