This is a staging area for visualizing sensor data on iOS devices by doing a bit of 3D coolness with CSS3.
Incident force (i.e. acceleration) measured in the device reference frame:
The following are (no sensor found)
Tait-Bryan intrinsic Z-X'-Y" angles.
On iOS (as of 6.1), alpha is a relative heading, which will accumulate drift error, while beta and gamma are auto-normalized based on gravity direction, and are therefore absolute readings.
The compass heading is also an absolute reading; arrow points North.