This detector clips on to the road angel compact, and works in exactly the same way as the built in laser detector does in the new road angel. You can buy additional sensors for the number plates.
I think it depends on where the laser targets you from, if its from close range then they can target a a specific part of the vechicle i.e number plate where as if it is from long range then they will target the front of the car so the laser will pick it up