Funny that this came up today, i was looking at info about it this morning.
Dension (
http://www.dension.com/main.php or
http://www.densionusa.com ) have a good looking system called ice link plus that connects to a large range of after market head units and a few factory units.
Another option is that Alpine (
http://www.alpine.com/ ) have their own adaptor (KCA-420i) to allow an iPod to be connected.
Both of these systems allow track selection by playlist, artist or album. both will display track information on the head unit if the head unit is capable, both charge the iPod when connected.
I will be getting something like this very soon.
