motion sensor with high pitch noise?
The latest craze, since they are legal most everywhere, is ultra-sound animal repellents. If it hurt your ears, imagine what a dog or cat feels. Farmers and those with a lot of land can legally buy pain field generators, much like the military uses.

It is 100 to 2,000 watts of ultrasonic waves. They are triggered by motion or sound and MUST shut off after a few seconds. The local police can intervene if it runs non-stop and the neighbors complain. The sound can travel 300 yards even in residential areas, and can be heard through glass windows.

Some offer options like a 'bark' detector for noisy dogs, and bright flashing LED's that cats hate.