Curiosity, Thoughts and Whatever...

While I was driving today on the road, it hit me of a very good invention. Why don't technologist or some inventor come out with a signal/turn sensor ?

Many people I notice are just too lazy to flick the left/right turn signal on the steering wheel, so what if there is a sensor that detect a certain amount of turn and thus put out the signal itself. Why not ?

In fact, all the technology are readily available and therefore it's a matter of integrating it. In future cars, there is no need for the manual turn switch. Or how about a voice activated turn signal capability ?