Don't laugh...But I actually bought a Jupiter Jack about 8 months ago after an Informercial...I couldn't get it to work with my WinMo phone at the time because the phone didn't have a 3.5mm jack.

However, it works GREAT with my Captivate. Plays beautifully through my car's stereo system.

Since it worked so well, but running off batteries, I actually purchased a similar device that can be powered by the lighter...and I also bought a dual-lighter converter so that I can charge both my phone and the AM/FM jack (both from Cellphoneshop.net, if you care).

What I like most is that if I'm playing music through my Captivate and using my GPS, everytime GPS speaks it's turn-by-turn directions, the music goes down (like on a telephone call) and the GPS directions are spoken through my car speakers -- then when the GPS finishes speaking, my music volume goes back up.

So much better than playing music from my CD player when using GPS as the phone automatically turns the music volume up down while using my Jupiter Jack/ligher-powered jack.

 

I don't believe any sound will come out of the usb port, only sound would come out of the headphone jack.

I have VW with an aux jack and I plug it into the phone and Pandora plays perfectly

 

You can always try bluetooth, if your car has bluetooth. I believe I read something on cnet that this works, but the quality may not be as good