Today I found very useful application at thinkchange.cn, that turn your Nokia N97 into a magnetic compass.It utilizes the inbuilt digital campass of Nokia N97.You need to "Calibrate" -- Rotate the device around all axes in a continuous movement to get a good signal before using.

To download the application, head on over to Thinkchange.cn.
Tip:- calibrate your compass when you start the app for best usage.

Phones Supported:-Nokia N97, 6210, 6220