It's possible and it's easier now.
Apple just rolled out its CarPlay iPhone connection for cars at the Geneva Motor Show this week with Ferrari, Mercedes-Benz and Volvo demonstrating the application, and 13 other automakers also signed on to ship “down the road.”
CarPlay works by replicating the iPhone interface on the car’s center stack display. It uses the car’s built-in controls and takes orders from Siri as well. And, it goes far beyond Siri Eyes Free. 
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