Android: How can I get the facing direction of the phone and the angle of view

I want t开发者_开发知识库o calculate the overlapped area between two phones, so I need to know the facing direction of the phone and also the angle of view of the camera. Does anybody know how to get these information? Thanks!

Following is an example:

\ \  / /
 \ \/ /
  \/\/

camera1 camera2

You could try to use the compass to acquire that information but not all phones have it... it probably won't be that precise either.