Meet the Boost Band: a wearable device you can rely on to charge your smartphone on the go. This wristband has a 1500 mAh inside to charge your iOS/Android devices. It has a circuit with Mini USB input and USB output, so it can be used to charge wearables, cameras, smartphones, and other portable gadgets.
The above video shows how the band works. You can find out more about it on Kickstarter.