A laser and a camera on one two-axis pivot. It points at a thing, then looks at what it pointed at. Everything else in the box exists to power that and aim it.
Seven parts, all off the shelf. Drag to turn it, pull the slider to take it apart, hover a part to isolate it.
Two servos and a bracket, because a pivot you can take apart is a pivot you can debug. The point is not the mechanism — it is that pointing and seeing happen from the same place, so the device always knows what it just did.