I don't understand the concept. So you take your mobile device with a screen, plug it into another, slightly larger screen, and then use voice commands that don't require a screen.
??
The car should plug into the mobile device (preferably over Bluetooth), not the mobile device into the car.
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CarPlay is to cars what iTunes was to phones...
http://www.engadget.com/2005/07/03/say-hello-to-the-motorola-e790-apple-itunes-phone/
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a better approach
http://www.automatic.com/
A) Bluetooth does not have enough bandwidth.
B) How do you keep the phone charged without plugging it in?