In spite of the claims made on their commercials & info-mercials, these products DO NOT WORK. Think about it...would all those pest control companies still be in business if those contraptions were effective? (Seriously, take a look in the yellow pages under "pest control".)
Here's the url for an opinion written by a professor at the university of arizona. You'll have to cut and paste it to your browser. There are others but they all say the same thing.
http://ag.arizona.edu/yavapai/anr/hort/byg/archive/ultrasonicpestcontroldevices.html
