My son and I had some fun tweaking our 2010 Audi A4 using a $30 cable. None of the changes affect the performance of the vehicle; they’re more geared toward entertainment, exterior lighting and window controls. All we had to do was install VCDS, the program that came with the cable, connect the cable to the diagnostic port under the dash and start modifying the configuration. Some of the tips came from AudiEnthusiasts.com, a great collection of information.
Overall, it was a pretty simple process and relatively inexpensive.