The script below is triggered every day from my Mac. I use Hazel to move the tar.gz to an external hard disk once it's finished. This happens every day without me noticing. You can exclude folders if you want to. You probably want to exclude giant cache folders.
You should have a similar script.
Curious: How you get it to ssh login without having to enter a password? I know I've seen people do this, but don't remember how.