Audio over USB / Custom car kit

[dcohn]

I have a Samsung Moment, and a Hyundai Sonata that has a USB port that puts out 5V and a 3.5mm aux input. What I want to do is get (or make) a USB cable that will allow me to charge the phone from the USB, output the audio through the USB port to a piggy back 3.5mm out to input into the car's input, and either have a microphone built in or accept a mic input that I can mount to my visor. Has anyone heard of such a cable? Does the Moment even support audio out over USB. What about forgetting the audio out over usb and just finding a 3.5mm cable that will let me output the audio to the car and has a mic?