Ford is set to release a management system that will restrict certain aspects of a car's performance based on which key is in the ignition. The speed is limited to 80 mph, you can't turn off traction control and stereo volume can be set to max 44%. It's targeted for teenagers and can result in getting a discount on your insurance.

The special keys will be introduced with the 2010 Focus coupe and will quickly spread to Ford's entire lineup.

Link: http://www.autoblog.com/2008/10/06/ford-introduces-limiting-mykey-for-worried-parents/