[LukaszB]

Could anyone possibly shed some light on what is used for measurement? gyro?

[dclowd9901]

I was actually beginning work on a similar project. Essentially, it's using a combination of the accelerometer and the gyro to get the phone's position in 3D space. That is, when the accelerometer capture lateral velocity, it knows it's moving in a certain direction at a certain speed (until, of course, it receives an opposite velocity, at which point it stops).

[untog]

Did you ever manage to get it to be accurate, though? I tried something similar but the accelerometer and gyro were nowhere near accurate enough.

[joezydeco]

How does it measure the length of the wall by holding it in just one spot in the middle?

[unwind]

Yes probably, but I would be surprised if it isn't also integrating over the accelerometers' output. See http://en.wikipedia.org/wiki/Inertial_navigation_system.