It's been exactly 5 months since I bought my iPhone, I've been waiting to buy some accessories to use it in my car (a FM Transmitter) to listen to music. So far, all the accessories that have come out are cases, cases, power chargers, headphones. No accessory that I know of, uses the iPhone Dock Connector port to do anything.
Of course, you can use your iPod accessory but that means turning the phone part of your iPhone off and put it in "Airplane mode". Apple touted their "Works with iPhone" when they released iPhone but so far, I've not seen a single accessory with that label.
So, apple, whats up with real iPhone accessories?