From the mbworld.org forum:

"Dension Ice>Link Plus (Mercedes Ipod Integration) Install and Review
Today I received the Dension Ice>Link Plus from Dension USA. The Ice>Link Plus allows integration of an Ipod into the Mercedes fiber loop which means you can control your Ipod from your radio head unit and retain steering wheel button control as well. The Ice>Link Plus will also charge your Ipod while in use which is a nice feature. The downside is you lose your CD changer as the CD Changer button on your Radio/COMAND becomes the button for the Ice>Link Plus Ipod interface. Additionally the power and fiber cable that goes to the CD Changer is used for the Ice>Link Plus interface."

http://forums.mbworld.org/forums/showthread.php?t=93278
Dension Ice>Link Plus (Mercedes Ipod Integration) Install and Review

He indicated that there was a passthru channel from his trunk down to the center arm rest...