Ubertooth One is a cheap, open-source Bluetooth network sniffer. Unlike Wi-Fi, which has had a wide range of free network monitoring tools for years, Bluetooth has remained pretty closed. Michael Ossman is about to change this, with his Ubertooth Kickstarter project.
The Ubertooth One is a USB plug with an antenna, and a ARM Cortex-M3 processor-based board in-between. Plug it into your computer and you can use it with various wireless monitoring tools like Kismet. The Ubertooth allows you to use Bluetooth in monitoring mode. This