How about something like Google Drive? Won't that keep folders in sync via a master copy on the net?
Imagine, you update and save Sketch 1 on PC1. Google Drive re-syncs teh changed file. PC2 sees updated file on Google Drive and re-syncs back down. Result = PC1 and PC2 in sync.
Would this work in that context?
The bonus would be a cloud based back up of all your files.