A shock sensor is alot better than a motion sensor IMO. If a big rig drives by and blows the wind by your car a little it will go off. Just set your shock sensor to the point to where if you hit your diver or passenger window, it will go off. Dont want it going off when a cat jumps on the hood. A motion sensor will not go off if the window is broken. Nor will the glass breakage go off if they hit the car. Or tried to jacl your wheels.