It would likely depend on what kind of car and audio system you have. Most newer vehicles will automatically integrate the iPod either by connecting it to the vehicle with a regular 30-pin connector, or, they will work nicely via Bluetooth.
The Ford MyTouch and Sync technology allows you to control your iPod with your voice, and the new Chevrolet MyLink technology does the same with Siri on newer Apple products. In other vehicles, your mileage may vary. Very basic controls seem to be pretty common with a high number of vehicles, regardless of price.
