A good start that would be trivial on ALL smartphones would be to simply notify when the camera and mic is active by using an icon. This is already the case for Location services, I can't see why it could be used for audio/video recording. Add to that an Audit log where I can see that application so and so used the camera at time X, and I'm at least able to tell whether I have been spied on after the fact so I can get rid of the application in question.