We talked about this stuff here several years ago. Now, like everything else, Moore's "law" and wirelessness have had their effects on things...
Cheers,
RAH
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http://www.technologyreview.com/articles/print_version/prototype0703.asp
Wireless sensors listen for gunfire. (Photo courtesy of Proxity Digital Networks)
Shot in the Dark
If a gun goes off in an abandoned junkyard, does anyone hear it? The police do, at least in the handful of U.S. cities equipped with gunshot detection sensors, which listen for weapons' acoustical signatures and clock the arrival of sound waves to triangulate their origin. But these sensors must be plugged into telephone lines, meaning they can't be installed in out-of-the-way places, and a separate detector is needed every 300 to 400 meters to produce accurate results. Now New Orleans, LA-based Proxity Digital Networks is testing battery-powered detectors that can be clamped onto trees and poles and that communicate wirelessly with communications towers up to five kilometers away. The Tulsa County, OK, sheriff's department is testing the system, which transmits information on the location of gunfire to officers on patrol. It can even identify specific types of weapons, which helps police "dispatch a more effective response team specific to the situation," says Tulsa County !
sheriff Stanley Glanz.
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R. A. Hettinga