I've added support to sync your sqlite files to dropbox automatically. I've tested on windows 10, ubuntu 15.10 and openelec 6. You can configure your dropbox account from the addon configuration. Go to the database settings and click "Dropbox Auth Code". Follow the steps and your db should automatically upload to the apps/kodiwatchedlist folder on your dropbox account.
There is a problem on Ubuntu 15.10 with they python-cryptography package. If you run into you have to remove the package with apt-get and install 'cryptography' with pip. Something like:
sudo apt-get remove python-cryptography
sudo pip install cryptography
Anyway, if anyone wants to help me test, my version of the addon is available from github here
. Before installing, you will have to remove your existing watchedlist addon.