Toyota in New Zealand needed a way to demonstrate the agility of their super compact Toyota iQ car so they turned into a four wheeled computer mouse that could move a cursor on a giant screen and operate a desktop computer. They did it a lot like motion capture that is used in 3D animation where a camera captured the car that had a light strapped to the top of it. Software interpreted the data from the camera and translated its position into X-Y co-ordinates. The co-ordinates were then sent to a second laptop 30 times per second which read the data and moved the cursor in real-time. The image on the second laptop was then projected onto a large screen.
The whole thing is reminiscent of the BMW Expression of Joy campaign where they used a Z4 as a paintbrush but in this case they went for something more revenue centric by using the car to create a print ad for the car itself. You can see the whole thing in the video above or at their microsite and they have made the code they used to create the event available to everyone as a free download.