I'm a little skeptical of those. I live in a deer infested area, and local stores sell devices that you put on the front of your car that are supposed to keep deer, and other wildlife, from running out in front of your vehicle while driving-- it's the same premise in that it emits a low frequency designed to deter animals. A friend of mine had them on the front of his SUV and he's tagged a couple rabbits, deer, and a possum since then. I honestly think those companies rely on the fact that statistically most people will not have issues with animals even if they're using a shoddy device designed to deter animals. But that's only my opinion-- to each his own. If you do use it and it does work, please let me know. I'm always looking for nonlethal deterrents. Cheers.