Unison is a two-way command-line sync utility that is supposed to be easier and better than rsync.
You can find a ready-to-deploy DroboApp package here: http://www.droboports.com/app-repository/unison-2-40-63
Many thanks to forum user iwsbarker for cracking this tough nut. I just took his work and packaged it nice and easy for everyone else. Enjoy!
As usual, comments, suggestions and feedback are welcome.