I have a car stereo that like many others will easily play a iPod or iPhone via the dock connector and usb. I don't choose music off the iPhone via the deck but I could if I preferred. I do have basic controls such as track forward and track backward though. The deck won't recognize a Samsung Vibrant at all.

Would it be possible to write a code that would cause an Android phone to get recognized as an iPhone or iPod for the purposes of audio output and basic control?

It is possible, but not likely to happen. The only way it would happen is by rooting your phone and altering the way your phone `handshakes` with the USB host.

The Palm Pre did SOMETHING like this when it first came out.
http://www.precentral.net/apple-blocks- ... es-syncing
Apple is pretty anal about their products, and quickly updated their software to stop this.

However, by reading your post it seems like your car stereo is using the apple accessory protocol
which controls things like volume, track, etc... Which there has been a few people who have cracked into.
So if you`re ambitious enough you could play around with that:
http://nuxx.net/wiki/Apple_Accessory_Protocol

drseamus sounds interesting, keep us posted what you find/do!