What is Reddit's opinion of Ultrasonic Rodent Repeller Direct Plug In: Save with Set of 3 Single Speaker Units with Unique SWEPT Frequency?

From 3.5 billion Reddit comments

I think there's a thing they sell that you plug into the wall and it makes a noise that is annoying to them (so they don't enter the room). I'm not sure what it's called and I've never used it but I know people who have and the mice in the dorms never got inside.

Edit: example http://www.amazon.com/Ultrasonic-Rodent-Repeller-Direct-Plug/dp/B003MHX1PY