Read the above link. You are crazy to trust it for secure communications.
The recent rains had washed away most of the smog from the usually murky Los Angeles skies, so we could easily see the giant high-rise buildings in the financial district. For the purposes of the shoot, we hooked up the BlueSniper gun to a laptop computer, instead of using the Gumstix computer. This allowed us to see in real-time the Bluetooth devices that were detected.
John pointed the BlueSniper at the AON building, which was 0.6 miles (just about 1 km) from our position (this distance was verified by GPS after the shoot).
It didn't take long for the MAC address of Bluetooth devices to appear on the laptop's screen. After a few seconds, John pointed the gun at the Library Tower / US Bank Building, which is the tallest building in Los Angeles. The building was .75 miles (a little over 1 km) from our position.
As more Bluetooth devices started appearing, John said, "This building is full of Bluetooth! Look we got some Blackberries!" He also explained that, with multiple guns, it would be possible to track a single Bluetooth device as the person walked around. In less than a few minutes, twenty devices were detected—all at distances over a half mile away! We decided to quickly conclude the scan, given police activity in the area earlier in the day from a bomb scare.