I'd go with coastal tech's
http://www.coastaletech.com/ULTIMATE%20IPOD.htm
This kit give you access to your ipod via the touch screen.
Don't forget to replace that 12V lead acid crap battery with an Optima D51. I'll be doing this today since I already have my battery and my cable kit should be delivered today.
in my 2008 Prius, there is an aux input for external audio sources like the ipod or other mp3 players. This aux input lacks ground noise isolator transformers. I took care of that problem though and eliminated the annoying sound that was being produced when I used that aux input by building my own ground noise isolator. now i have a switchable 3 source selector into my aux input.