Apple
Apple has officially announced CarPlay, a means of natively bringing your iPhone's capabilities into the car.
As Apple puts it, CarPlay "takes the things you want to do with your iPhone and puts them right on your car's built-in display."
This means you and passengers can send and receive email, texts, use GPS navigation via Apple Maps, and more. Of course it has Siri capabilities so that you can interact with it by voice, but you can also use your car's knobs (for adjusting the volume, example) or your car display's touchscreen. Apple says that if a certain control normally operates your car's display, it's compatible with CarPlay.
There's no announcement yet on when we'll see this available, but Apple has shared some cool teaser shots on its site.