The Porsche iPod interface (usable through PCM) is available now from Porsche. I'll get one of the first units installed in my 997 Turbo as soon as shipping starts, it may take a week or two though, maybe longer.

Just in case it hasn'r been mentioned.
It is also available for the Cayenne.

Btw: all non-factory approved adapters which interfere with the electronics of the car may void your warranty for the whole electrical system of the car, incl. some black boxes. Just mentioning it...