So after my Kensington LiquidAux adapter crapped out on me, I decided to make my own car solution. Without getting into details about why all other options don't work for me, I'll just say that this is the only solution I know of to get power, audio, and control through the dock connector. It's not the prettiest solution, and it has the one bug of the car shutting off doesn't stop the playback on the iPhone, but i think it works pretty darn well, and the piece that gets the most wear and tear is easily replaceable. Also as a side note, Apple's little remote is one of the most powerful IR blasters I've ever seen, I swear you can be under your desk pointing it at the carpet and it will somehow bounce around and hit your Mac sitting on top of your desk.
Parts list with approximate cost:
iPod dock(had it laying around, retail about $30)
Apple Remote(got one used off amazon for like $2)(
iPhone Car Charger(no name brand from Fry's $12)
iPhone Dock Extension Cable($15 from Fry's, this was the key to the whole shebang)
Velcro One Wrap(couple bucks, but I had some around the house)