Are you just after audio or you want full video playback too? With or without integration?
Just audio? Audi do the cable (for about £100) or there are some equivalent cables on eBay for about £20, I think.
This is stupid money, but the
Alpine KCE-425i is amazing: £200-ish online (
CarAudioCentre) plus £? for wiring looms and then do the VIM hack and fitting yourself or if you're lazy,
£380 from HazzyDays fully fitted. This gives does audi + video and gives you pretty much FULL control of your iPod via the RNS-E controls (and some control, inluding tracks, etc via the steering) - just chuck it in the glove box and leave it charging.
Even more stupid money which will give you a slightly LESS integrated, albeit much broader product, would be one of the Ampire video adapters: I've got the Freeview+ tuner in mine (the TV part which is fully integrated), which takes any sized USB pen drive and plays videos and music off it... AND has two video lines in: for an iPod/iPhone, incl video and lord knows what else (PS2 slim?): (£450ish+fitting or £600-odd fully fitted, with VIM hack, etc)...like I said, stupid money.
I was going to ditch my "basic" iPod AV+charger lead for one of these iPod AV+remote docking stations from
Clas Ohlson, so when the iPod is sat in the dock in the glove box, I can control the video / music via the remote.
Probably a step too far as the Ampire unit already does everything I REALLY want the RNS-E to show (and handles more video formats), but I may be tempted eventually.