Ultrasonic Mouse Deterrents are used as non lethal ways of keeping mice away from your house or cottage. What's great about using ultrasonic deterrents is that they keep other rodents away like squirrels, rats and bats. Ideally you would want to use this product in a cottage or garage because there could be some light ringing or clicking noises that will get annoying after a while. Even though it's supposed to be only heard by animals you will hear something.
Here are examples of ones that I've personally used.
Again not bad for the price but beware of the clicking noise.