We just finished a 2000 mile road trip with multiple gadgets that we wanted to plug into the cigarette lighter plugs (MP3, Laptop, DVD player, cell phones…) and it reminded me how much I hate cigarette lighter plugs. I’m always having to fiddle with the plug to keep ‘em working…
I drove for 100 miles or so thinking my mp3 was charging, only to find out it had stopped after only charging a little.
So, I appreciate what you’re trying to do.
I think the easiest approach would be to try and find a powered USB hub that happens to uses a 12V ‘wall wart.’ If you could find one, it would be simply a matter of cutting the cord at the ‘wall wart’ end and wiring it up to a fuse.
Then, of course, find a place to mount the hub.
Make sense?
LATER THAT SAME DAY
What I'm thinking about is something like this IOGEAR hub:
but you would need something that has a 110-to-12V adapter. That info is difficult to divine online, so you would have to go to a large electronics store and search what they have.