geolocation + camera

I am developing an application that turning the camera I go showing landmarks in the distance (something like does google glass) and would like to see if anyone knows how to detect to what extent is pointing the camera (or device) .

Any help about how I can get the direction of the camera? maybe something like a compass?

I'm developing in AIR with AS3 and for the moment only going to be for Android.

Sorry for my english.