If the virtual button is occluded by moving the camera so it is partially out of view, the button will still be triggered. This shouldn't be happening. It is known where the camera is in relation to the marker and it's virtual buttons. So the software can test whether or not the button is fully inside the camera view frustum, partially occluded by it, or totally out of it.
I know I can write such a filter myself, but wouldn't it be more appropriate if it is included in the SDK?