This is an interesting project where we have used a toy car to control it through the bluetooth of your cell phone. We have used the arduino board in this project.
In fact Bluetooth controlled car is controlled by using Android mobile phone instead of any other method like buttons, gesture etc. Here only needs to touch button in android phone to control the car in forward, backwardd, left and right directions. So here android phone is used as transmitting device and Bluetooth module placed in car is used as receiver. Android phone will transmit command using its in-built Bluetooth to car so that it can move in the required direction like moving forward, reverse, turning left, turning right and stop.
Check here the full project with circuit diagram and code: Bluetooth Controlled Robot using Arduino
