I found the iSimple PXAMGA Media Gateway for Ipod control through the stereo. It's probably as good as it'll get without adding screens. It would be limited to the stereo's screen and get by with simple controls, playlists, genre, artists, and I think albums.
I'll have to check on the Parrot CK3000 plus PAC adapter to see if I'll be able to use bluetooth through the stereo and phone button without adding the visible Parrot controls.
I haven't had time to look into it, but maybe I could use a wifi Ipad tethered wirelessly to a second phone if I wanted the unlimited bandwidth ipad option.