As one of its daily deals, PricePlunge offers the Doberman Infrared Home Defender
, model no. SE-0104, for $8.99
for shipping. That's the lowest total price we could find by $4. This motion-detecting sensor protects an area 60 degrees vertically and 60 degrees horizontally from the unit with 95-decibel alarm. It requires a 9-volt battery (not included). Deal ends today.