HC06 are popular Bluetooth to Serial modules bases at CSR BC04 Bluetooth technology. They have with build-in 2.4GHz antenna, support Bluetooth class 2 power level and operate with voltage in range 3.1V~4.2V
If you want to add Bluetooth wireless connectivity to your next device without hassle with Bluetooth protocol, HC06 will allow you this working as simple as with UART. The module have AT commands to listen and pair to other nearby BT devices, then you exchange data like if you worked with wired uart.
Tons of Arduino examples are available on the net. The module is made to be easy soldered on your own custom board.