Ener-watch, an Italian startup, has realized a pocket-sized powerbank for Apple watch and main Android smartwatches, as LG g watch r, LG Urbane, Moto360 1st and 2nd edition, Huawei classic , Samsung gear S and Samsung gear S2.
It is lightweight, capacity til about 7000mah, so you can charge your smartwatch more than 10 full times, external usb to charge your smartphone and also a small torch. Ener-watch will be available for presale on Kickstarter/Indiegogo from June.
infos on http://www.ener-watch.com
and also on https://www.facebook.com/ener-watch