No idea about the car setup, but I definately know that an iPod Nano setup is possible on a RIB.
I have this waterproof case...
http://www.marine-audio.com/Products/H2O-Audio-iPod-Cases/Nano/An-iPod-Nano-Fully-Waterproof-''H2O-Audio'-Case_1.htm
...although it appears to be available a bit cheaper cheaper here...
http://www.sailgb.com/p/ipod_nano_fu...terproof_case/
...with a setup similar to this...
http://www.marine-audio.com/Products...ut-Adapter.htm
As I am a girl and rubbish with most things requiring wiring or electricity, the nice Ribcraft boys sorted it out for me

, but I'm sure you clever boys could do this yourselves...