I have a 2005 Audi A4, I can't remember the manufacturer but I managed to find an aux in solution that plugged into the back of the head unit as a second CD source. Now that I have an iPhone I can connect phone through bluetooth and audio via a 3.5mm jack.

My wife has a 2010 Volvo XC60, the iPod connection takes control of the ipod fine if you leave the device plugged in; it restarts play at the point where it was switched off. If you're unplugging your device (as in an iPhone) then you would have to manually get back to wherever you were in your chosen playlist.

Luckily it also has an aux in but then you're not charging the phone...

I don't believe Audi or BMW do an aux in with their newer models, just an iPod connection, so no idea how I'll listen to my iPhone podcasts when I change to a new A4 or 3 series.

I find it shocking that integration is still so poor. It really shouldn't require additional hardware.