I think all new cars should come with USB charging ports in the glovebox, near the dashboard, and in the back seating area. I found a handy USB charging port in a 2012 Mini that I used to recharge my Nokia N8.
We carry six devices that often reach the end of their duty days before we park the car on weekend drives. On many occasions, I've just toggled off the data services on the handsets and that keeps the phones running for days. But sometimes you need data to see things, like with the Hauwei pebble that makes our car a wifi hotspot. It would be nice to connect that little device to always-on car power. David Savery has done just that, respecting the different colour codings on the device cabling.
Savery used a USB socket, a fuse, a switch and a 7805 voltage regulator which turns the nasty 12-14V output of a car's electrical system into a smooth 5V at up to 1A. That's good enough for most portable electrical equipment but might not be strong enough for an iPad. Savery notes "an input of about 7-35V DC will produce a nice flat 5V output with a current of up to 1A which is twice what a normal computer USB socket will output." He also installed a heatsink to absorb the warmth from the regulator when it pushes out 200mA.
If we keep our current car for another year, one of these USB charging points is going to appear in the glove box.
David Savery -- "The in-car USB charge socket" on the R2UK blog, February 28,2010.
Instructables -- "How to Make Your Own USB Car Charger", 2006
Bernie Goldbach curates DIY links.