I’m really happy you added external sync. I tried SimpleNote but I found that I MUCH preferred MyWritingNook over SimpleNote. I’m not sure if you can do it or not but if you could add MyWritingNook as another external sync method then I would greatly appreciate it.
Unfortunately, I think they use their own network for synchronisation based on Google Apps. If the web portal version of the software allows easy access to your file system, you could link it up with your folder syncs.