Every now and then, something causes you to flail around like a crazy person while behind the wheel. Sometimes it's the jerk who cut you off, sometimes it's hearing your favorite song on the radio. Whatever the reason behind it, Google would like to take advantage of this gesticulating and let you control your car with it.
By mounting a camera in your car's ceiling and a laser in your dashboard, Google will be able to read and decipher any number of gesture commands. Swiping downward near your window will roll it down for you, while pointing to the radio will pump up the music.
It's an innovative system. It's also one which we likely won't see until Google's self-driving cars are on the market. After all, keeping your hands at ten and two doesn't exactly allow for much gesture-based shenanigans. Once those mitts of yours are free to move about the cabin, however, it looks like Google has already figured out how best to put them to use.