I have small kids, don't want to use traps or poison, so I am looking for an electronic pest repellent that really works. I purchased a few units from Black and Decker but after 30 days of use the mice haven't gone away.
" Electronic Devices
Although mice are easily frightened by strange or unfamiliar noises, they quickly become accustomed to regularly repeated sounds. Ultrasonic sounds, those above the range of human hearing, have very limited use in rodent control because they are directional and do not penetrate behind objects. They also lose their intensity quickly with distance. There is little evidence that electronic, sound, magnetic, or vibration devices of any kind will drive established mice or rats from buildings or provide adequate control. Despite their lack of effectiveness, many such devices continue to be sold through magazine advertisements and at some retail outlets."
from:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7483.html
You might want to read the whole article to get alternative treatment ideas.