[b-3-n]

Thank you for sharing this creative idea. "so that the fingers can touch (or almost touch) the screen" I think this is a big advantage of this approach since you can only achieve this with the back facing camera. On the flip side, with a back facing camera you either have to place the camera in between yourself and the screen which might be awkward or you have to ensure a placement of the camera behind you that isn't prone to occlusions (e.g. your head or chair might occlude your hands from the cameras point of view). The latter might also make calibration more difficult or impact precision since you might have to mount the camera with some elevation causing a less optimal camera angle.