Hi,
HC-05 bluetooth modules will act as a bluetooth slave where u can use your android or PC to pair with it and send character datas. you can controll the 4 wheels according to the data received to the bluetooth, for example you can program in this way when "A" is received you can make the motor to run forward using code in arduino or any micrcontroller. refer these links to get more ideas.
http://www.engineersgarage.com/contribution/android-phone-controlled-robot-using-arduino
http://www.engineersgarage.com/contribution/android-phone-controlled-bluetooth-motion-vehicle