It's only a prototype, but researchers in Japan have developed a car seat that can detect when a driver is about to nod off. The idea is to fit the seat with a buzzer, so that when the seat's built-in sensors notice a drop in your pulse, it'll sound an alarm to wake you up. The seat's creators expect to have a consumer version ready in five years. Overall, it's a cool idea, and I can find a lot more uses for this kind of chair than just inside a car.
Smart Car Seat Detects Drowsy Drivers [Pink Tentacle]