Worn on a collar or mounted on a wall, the Dog Bio Security System translates barking into alarms for police or military. Bio-Sense Technologies spent two years capturing the sound waves of woofs and arfs, encoding them to be read by a digital signal processor. All dogs emit the same type of bark when they sense trouble. The device can distinguish this bark from a dog's "Hello." A consumer version costs $100. A high-end version costs tens of thousands of dollars but is still 25% the cost of video surveillance.
http://www.defensetech.org/archives/001966.html
