BLUETOOTH-SERIAL-HC-06 is popular easy to use Bluetooth to UART module
|10 - 49 pcs||5.36 EUR|
|50 - 10000 pcs||4.76 EUR|
It's very easy to add wireless serial connectivity for your device with this module. Examples for Arduino and other boards are available. Once you pair with other Bluetooth device you work like with normal UART to exchange data.