Oh cool. So I could probably use something like
trackIR.yaw = math.degrees(iPhone.yaw)
to automatically convert the iPhone's radians to degrees.
Tried out the whole package last night: DIY Rift HMD, War Thunder, and my iPod Touch 4G for tracking.
It worked really, really well. With the tracking, I felt like the HMD was a window into another world. I had a blast buzzing an aircraft carrier with tight, controlled turns, turns that you just can't do without the spacial orientation that head tracking brings.
Palmer praised the iPhone's sensors somewhere on MTBS back when he was working on the FOV2GO. He said they are very accurate with little drift. That's been my experience so far. I've never tried the Rift, but the fluidity and the responsiveness of the iPod was what I'd imagined when I read about people's experiences with the Rift. (I should note that I'm using an iPod for this, and I haven't noticed any of the stuttering or latency issues that some people have reported with the iPhone.) It seems one-to-one. I've noticed a little drift, but it always seemed to come after my poor little MacBook Air dropped frames in War Thunder (it ain't a gaming machine, though it does better than I figured it would), so it's probably not the iPod's fault. I think FreePIE uses less CPU than TrackIR, too — or at least, less than FreeTrack. What a great program.
Now what I'd love to do is to figure out how to use FreePIE and the iPod to mimic the Rift's tracker in all those Unity Rift demos . . . but I gather that no one has been able to trick the computer into thinking there's a Rift plugged in yet. Does that mean FreePIE's Rift plugin only works with the Rift as read, not write?