This module from Roving Networks is powerful, small, and very easy to use. This Bluetooth module is designed to replace serial cables. The Bluetooth stack is completely encapsulated. The end user just sees serial characters being transmitted back and forth. Press the 'A' character from a terminal program on your computer and an 'A' will be pushed out the TX pin of the Bluetooth module.
Note: These modules have been revised to remove three unused RF pads from the bottom of the module. For more information on what pads were removed and why, check out the change notes below.