For what it's worth, there is a recently formed Car Connectivity Consortium that has as one of it's goals to set standards for interaction between vehicle systems and devices like Android Phones, iPhones, iPads, Windows Phone, etc, etc.
Like most such endeavors it will probably take years to be fully realized and not meet all every "wouldn't it be great if" ideas, however it's better than nothing.
However, one company is not on that list. Can you guess which one? Pioneer.
The reason you see so many of these HU's support full iPhone integration, with coming support for apps, etc, is because of one thing: A single, well documented, standardized docking connector. Apple has rolled it out across their product line and published specs on exactly what it can and cannot do. No such specification exists for Android - if an Android device even has a dock (very few do) it's proprietary and exists primarily as a way to force you to buy that particular manufacturers charging cable. This is a situation that is unlikely to change any time soon. The situation is pretty much the same for Nokia, Microsoft, and others in the phone software business - only Apple controls their entire software and hardware design, specifications, and supply chain.
Thus, with Android, et all, there is a problem - how do you communicate information to/from the phone beyond audio? Sure, they have USB (most of them), and by golly you can do all sorts of things with usb on a PC...but it's not the same. At all. The software on the phone has to allow different types of communication over the interface, and publish those standards, and then the receiver side has to understand them. If each manufacture picks their own particular way of doing it, then you end up with only certain models/versions of phones working with certain model/versions of HU. The same situation exists for Bluetooth connections. This is one of the primary problems, by the way, that the CCC linked above wants to solve.
Sony may have figured out how to get basic on-screen Pandora support working over BT, but I bet it wasn't easy, and I am certain it's proprietary to Sony. The plain, hard fact is we are two or more years away from seeing widespread support for "Smart Phone" integration that doesn't involve Apple.