[Sandbox] electronic compass
 

As we all know the N900 has no electronic compass, but for some applications like astronomy apps and augmented reality it could be very useful to have the possibility to determine in which direction the device is facing.

Especially for astronomy programs like stellarium it would be advantageous that the compass also works if the device isn't in line with the horizontal level (or if it's possible the accelerometer data has to be used to calculate the right data)

An additional device must have a clamp etc to fixate on the N900. A electronic compass needs to be calibrated, with a clamp that asserts same alignment every time it is used the calibration process must be done only once.

Brainstorm Link

ToDo:
Read through this thread and collect usefull information/solutions:
http://talk.maemo.org/showthread.php?t=31861