Cool! Thanks for that link sunjan.
I should've clarified what I'm trying to do...
I installed a Pioneer Premier DEH-P600UB
http://www.amazon.com/gp/product/B0013NY8X8The USB connect works great with my iphone. It charges it and allows me to browse and play all its contents.
What I realized now is that sometimes when we are camping or on trips in my VW van, we like to watch DVD's on my powerbook...hence the need for a 3.5mm jack into the Pioneer head unit.
I'm still not sure if that device will work or not. The Pioneer USB may need to be activated somehow for it read in the audio, but I'm not sure.
The unit does have a 3.5mm aux in on the back of it, buy my install leaves almost zero room back there to even plug in a right-angle mini-jack...so I was hoping to use the USB.
anyway, thanks again, I'll buy one of these and try it out.