In a project funded by the United States Pentagon research facility DARPA, a pair of security experts, Charlie Miller and Chris Valasek, have demonstrated a method which will allow hackers to take control of a vehicle using just a laptop and an NES joypad.
Basically what it does is connect to the car's electronic control unit by way of the on-board diagnostic port, and allows the control of things like acceleration, braking, steering LED dashboard displays and even the horn. The two vehicles that they took control of in their tests were a Toyota Prius and a 2010 Ford Escape.
The idea of the project was to raise awareness of the increasing dominance of computer systems in modern automobiles, and one would assume their potential vulnerabilities.
Given that the project is being funded by the Pentagon, it seems unlikely that the major goal is something so altruistic as making people aware of a problem. That, however, is beyond the scope of this article and best left for a late-night tinfoil hat round-table discussion.