I fitted this ages ago and meant to post it but forgot. I thought some of you might be interested in the USB socket that I fitted to the handbrake console:
The console is in a state though and will get refurbed soon.
it's a neutrik usb socket and dust cover, cost about a tenner. it uses a standard printer cable and runs to the back of my head unit.
Kayjey's right I don't think many (if any) head units offer charging as a feature but the last two USB head units I had would also charge USB devices when I tried them; although I've got my other USB stuff hard-wired in already.