2. The second type of system used in cars to detect button presses is a simple and elegant voltage divider network. A voltage is run through a circuit that measures the resistance. Each button introduces a different resistance when pressed. The car's circuitry can deduce which button has been pushed and respond accordingly. This is elegant because it does not require a separate wire for each button to be run down the center of the steering column.

To decode the network and convert it into something your PC can understand, you need a device like this.
It converts the resister network inputs into remote control outputs. You can use an infrared receiver on your computer and software such as Girder to interpret the outputs and convert them into commands for your applications.