I been trying to find a better way to explain this to you, but somehow find myself getting too busy in my day.
Ok, the sensors in the controller uses something called roll, pitch, yaw. This is generally how you would aim a gun on screen without directly moving your wrist from the zero position. This is why the camera isn't needed for this. The sensors basically have this on lock. It deals with the twisting and turning (orientation) of the device.
For the camera, think of some imaginary cross hairs in front of you. Ok, now, if you will, hold your hand out in front of you, palm facing away from you, as if you were trying to signal someone to stop. Ok, without making any twists or turns to your wrist or arm, side stepping left, right, kneeling, jumping straingt up, stepping bacwards walking forward, THIS is what the camera tracks, which is the light bar. Here, you are moving away from the zero position on an XYZ plane.