This video tutorial below will teach you how to hack bluetooth headsets, step by step. The tutorial will show you where to get every application you need, and exactly how to install and configure necessary applications using a Linux terminal. After you've completed the configurations, and installations you'll be able to send and receive audio from bluetooth sets. You could either send audio to the headset, or listen in on everything being said. It's very possible, a friend of mine played rock music on another one of my friends bluetooth as a joke before. The look on his face when the music started to play was absolutely priceless.