Whilst it's good to be able to listen in on the action using our computer, we're dependent on having a network connection with the listening Pi, either through Ethernet or over Wi-Fi. This means it's not very portable or discreet, so wouldn't it be great if we could eavesdrop wirelessly from the next room or outside with just a Bluetooth headset or small speaker? Just like a bugging device.
Bluetooth is a short-range radio technology that allows wireless communication between devices such as mobile phones, computers and headset or speakers. As such, the Bluetooth system features an audio protocol as standard, which we make use of (called Advanced Audio Distribution Profile or A2DP for short). Standard Bluetooth gives us a range of up to about 10-20 meters between devices - enough to listen in from the next room or outside.
As an added bonus to make our system even simpler, the new Raspberry Pi version 3 boards include a Bluetooth radio...