Playlistmag.com has a well written review of the highly anticipated Alpine iPod interface. Here's an excerpt:

05

When used with a compatible Alpine head unit, Alpine's new $100 KCA-420i iPod Interface connection kit lets you play and control your iPod through your car stereo. Unlike BMW's popular iPod kit — which limits access to five playlists you specifically create for the system and limits navigation to skipping tracks forward and back — Alpine's solution lets you access all of your playlists and, via its onscreen display, search for songs, albums, and artists. (And the Alpine offering can be used in any car, not just a BMW.) After evaluating the KCA-420i for a month in my Honda CR-V test vehicle, I appreciated its features, innovation, and sound quality, but at times found myself frustrated by its interface.

You can read the entire review here.

If you can stand the garish look of the required Alpine headunit (all 2004 or later Alpine Ai-NET head units should work) and poor interface, it sounds like this might be a solution to consider.