Did you get a new Bluetooth headset for Christmas? If you did then know that it might be vulnerable to eavesdropping and audio injection.
Check out this video where Joshua Wright hijacks a headset of a custom inside Starbucks while standing across the street from the coffee shop.
If you're interested, one tool he uses is called Carwhisperer and you can get that at the Trifinite.stuff Web site. It comes with source code and runs on Linux platforms.