I've created a folder w/ two subdirectories, "in" and "out". In "in", you put source videos at any resolution, in "out" appears scaled and prores 422 transcoded videos ready for offline editing. On the backend is a linux box running a coffeescript in node.js that fires off a multithreaded avconv to do the heavy lifting. It checks to make sure there's no .!sync extension. Works great, and the OSX Sync client gives you a little notice when your file is ready in the "out" directory. I almost don't want an API, so that I can resist temptation. I ilke that everything is done cleanly through directories, and I feel that it's a nice hedge against Sync going creepy someday, because if I keep it simple like that, I can imagine an open source alternative quickly appearing to take its place if it does.