LightInTheBox offers this OBD2 Bluetooth Wireless Diagnostic Scanner for $3.99 with free shipping. That's the lowest price we could find by a buck. It works with a free program that allows you to use your PC and a hardware interface to get the information from your cars computer.
Note: This item ships from China and may take two to five weeks to arrive. Uncheck "Add Shipping Insurance to your order" during checkout to remove the 49-cent fee.