A few weeks ago I heard some scratching coming from the wall cavity behind our TV. Not little, innocent mousey scratches but big, full-on, 'I'm a rat, I'm diggin' a home and I'm bringin' the family' sort of scratching.
I suspected no rat trap would be big enough for this guy, and I didn't really want poison sprinked around the house, so I ordered one of these gadgets.
Amazingly enough, a couple months later, no more scratching sounds! This is hardly unequivocal proof that the rat has been driven away for good (and who knows, perhaps he just felt like a change of scenery), hence the 4 stars rather than 5...but on the evidence available this thing actually seems to work.