This got me thinking of getting a flashlight as a Christmas present. Doing a little research and both Nitecore and Fenix now make a series with a micro usb plug built in to charge the battery. That's pretty cool. My smart phone has a micro usb so I have a charger in all the cars.
http://flashlight.nitecore.com/produ...gory/mh-series
http://www.fenix-store.com/uc-series/