I thought of this idea myself, and found "Dead Trucker's Handle" doing a search for prior art. There are some similarities, but some differences as well.
The Sleeper-Saver is intended to help prevent accidents caused by drivers falling asleep at the wheel. It is similar in function to the idea mentioned
(which I think is a great idea!), with some key differences. For one thing, it is not limited to trucks. This can be installed in any vehicle.
Rather than simply have a dead-man switch in the steering wheel, the Sleeper-Saver has a device which monitors the driver's eyes. If the eyes are closed for longer than a pre-set length of time, the steering wheel locks in place, the cruise control (if being used) is turned off, the brakes are applied until the vehicle comes to a stop, and the vehicle's hazard lights are activated.
The driver is woken up with a shrill, high-pitched alarm and an automated voice intructs him/her to pull the vehicle to the side of the road. At that point, a 5 minute timer is activated. Once the timer reaches zero, the engine is deactivated for 2 hours, preventing the driver from blundering on and endangering other motorists and giving the driver 2 hours with nothing to do but rest.
In the event that the driver absolutely *must* start the vehicle before the 2 hours is up (say, somebody is trying to hijack him/her) a manual override switch may be flipped, staring the vehicle but activating a GPS beacon and alerting the police.