Camera shutter click

I don't believe you will be able to detect such a thing, since the camera app is separate from your own mobile app... 

However, if you app is talking to the camera, there may be some sort of pingback that the developers can read....

Sort of like the purchase module.. we can't read the purchase popup directly, but a successful purchase will return an success to the app upon purchase, so we can track successful purchases within our app, even though we don't have direct access.

You should talk with your mobile app developers to see what they can and cannot do.

I wonder would it be any easier to track the result rather than the action here? For example if you are using the camera to take a picture, track that a new image was added to the app and specify the source of the image rather than tracking the actual camera action.