Features:

• The use of a DC-DC converter, allowing the board to be powered with a minimum of 1.2 V, but with a maximum of 5.5 V. Higher voltages or reversed polarity in the power supply will kill the board. 
• A surface-mounted ATmega168 (as with the Arduino Mini). This doubles the amount of space available for your sketches and adds three more PWM pins and two more analog inputs. 
• Pin 7 is connected to the reset pin of the Bluetooth^® module. 
• Only use serial communication at 115200 baud; this is the speed that the module has been configured to use.

The Bluetooth^® module used is the Bluegiga WT11, iWrap version (details and datasheet on the Arduino page). The Bluetooth^® module can be configured with commands set over the serial port from the ATmega168 (see the iWrap user's guide for details). A program to set the name and pass code of the Bluetooth^® module is run once on each Arduino BT. The name is set to ARDUINOBT and the pass code to 12345. For complete details, see the initialization program's source code. The ATmega168 comes preloaded with a bootloader that allows you to upload sketches to the board via the Bluetooth^® connection. The bootloader source code is available in the Arduino SVN repository.

Arduino Bluetooth^® Datasheets