Use your Symbian OS mobiles to control devices through Bluetooth.
An serial to Bluetooth converter is used in this project.
The Microcontroller At89C2051 is used to receive the data from the mobile through bluetooth.
Most of the Nokia smartphones can be used in this project.
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
The mobile app is written in python language. The download contains the python code and the microcontroller code.
More images here.
8051 Device control through Bluetooth using Symbian OS Mobile Phones 1.0
Device control through Bluetooth from Symbian OS Mobile Phones