Here's the another design which uses AUBTM-22 serial to Bluetooth module.

The only difference from the sparkfun module circuit is, this module works on 3.3v so the microcontroller is also operated by the 3.3v power supply.

The module have a default baud rate of 9600, so you have to change the program, since the Sparkfun module works on 19200 baud rate.

The pairing code for this module is 8888

Download the assembly code from here