With this keychain fob-sized backup battery from mophie, you’ll have 1000mAh of reserve power right in your pocket. The juice pack reserve micro has built-in cables, USB to charge itself and microUSB to charge your smartphone or other small device, so you don’t need to carry cables with you. The lithium-polymer high-output battery charges your device quickly, and there’s a power indicator button that shows you the backup battery’s charge status. There’s no power button – smart technology automatically turns the battery on when you plug it into your phone and off when you unplug it. The juice pack reserve micro is $39.95 at mophie.