i recently did this also
when i bought my phone from t-mobile, i had my friend who works there huck me up with a extra usb sync cable
the connection that connects to the phone has 2 philips screws on it. if ur careful enough u can take it all apart to the point of getting to the pins / wires
the usb cable with the power inlet on the back of it up by the xda connector, has enough wires in it to cover you for audio left and right and mic + if u use a common ground (1 ground across all 3 connections)
this is important to know when your alpine cva-1004 uses a common ground and wont engage the video unless all 3 wires are grounded
anyways... i was able to use a ginsu kitchen steak knife (sharpest knife i had) to cut away the rubber shielding on the actual wires holding the wires to the pins. otherwise u could use ur soldering iron and just burn threw it, just try not to breath it in.
then u just un solder the wires, reroute them to the right pins. if u want, use some hot glue to seal them back up, but if u solder them strait enough, the casing will protect it enough
then clip off the usb end, i took a spare component PS2 video cable, the wires were thin enough to integrate nicly into the usb cable, clip that, strip it, solder those in. clean everything up with some black electrical tape and ur done
mine ? my alpine cva-1004 has a remote mute wire. plug the phone into the aux in on the radio in the car, run a mic cable and audio cables (or use speaker phone) and u have the closest thing to a in car cell phone.
also works nicly for listening to mp3s in the car, but my xm satelite radio has that pretty nicly covered
just my 2 cents, but its not hard. i didnt wanna screw up the cables, so it took me about 2 hours in total to do a nice job.