heres are some more options on i-pod integration
http://www.dension.com/icelinkfm.php

this one works on the CDR23 radio used on the Cayanne and maybe the NAV Crossfire, http://www.dension.com/icelinkgateway500.php

I need to check into the NAV radio and see if that one has the fiber optic port, which I think it does.