What we needed:
The ability for multiple developers (1-3), working on the same projects, from multiple remote locations and various local environments (windows/mac), to have simultaneous access to a shared workspace, with the ability to push to production.
Obviously things like Git and SVN are industry standards, but a bit difficult to use with Shopify. One of the major complications is that as a fully self-hosted backend solution, you can't deploy a local Shopify instance, and you can only push to production via the API.
Themekit is a utility that can monitor for changes in a local repository (aka folder), and then push those changes to a theme, production or staging (aka live or unpublished).
Essentially, the jist is this:
Use the Google Drive Local Application (avail. for windows & mac) to keep all the local folders synchronized across developers, taking advantage of google drive's basis version control (more appropriately called revision history - it isn't a true VCS, there are no branches or merging or anything like that). Theme watch is run out of the same local folder which pushes updates to the server. So up and down is controlled via themekit, and side to side is controlled via Google Drive.