Guy Plunkett shared a DIY portable wireless charger for the Apple Watch, using an Adafruit Powerboost.
Pocket Sized battery powered charger for Apple Watch.
it has a 2000mAh battery which should provide a good number of recharges of the watch. It’s self can be recharged using a micro USB cable.
The circuit board is from Adafruit, 500c. I cut the Apple charge cable and directly soldered it to the 500c. Red is +5v, white and green need to be shorted together, and shield is ground!
Check it out; https://blog.adafruit.com/2015/05/14/diy-apple-watch-charger-by-guy/