2013-09-07, 15:53
The XBMC Backup addon already runs as a service and can use Dropbox as a target. Not saying this addon isn't needed for other types of files you may want to sync but settings/addons/etc can already be backed up via this addon. You might want to check it out if you're looking for something to just backup your settings data. The setup is basically the same as outlined for this addon to get your dropbox account authorized by the addon.
http://forum.xbmc.org/showthread.php?tid=129499
http://forum.xbmc.org/showthread.php?tid=129499