As you saw from the project schematic in the last entry, there is always a micro USB from the powerboost charging board to the pi itself. Which is constantly connected and will need to be inside the housing of the watch in the final product form. 

My micro USB cable is 1m in length, which will take up a lot of space/volume in the watch house, so in order to reduce the size needed to be the very smallest it requires, I have spliced this micro USB Cable to only a few inches long, i daren't go any shorted due to the intricacies of the wires and lengths when soldering involved. 

This involved, stripping the micro USB back to its constituent 4 wires ( power, ground, data (positive), data (negative)) and then soldering these back together as can be seen in the attached photos:

*NOTE: Not the best soldering I know...