This is the easiest way to have a long running script, running in a screen session notify you when it finishes (or when it totally craps out.)
$ ./long-running-script.rb; \ echo "Oh crap! Your long running script isn't running" | \ mail -s "Your thing died" email@example.com
Run it as a one-liner and stop compulsively checking on it.
If you don’t have a mail command you can install
mailutils on Ubuntu.
$ sudo apt-get install mailutils