There are several ways to accomplish things like this:
Using Atomics to kill the chicken
You could e.g. setup one of your Ubuntu machines as a Nagios server (or any similar service). There are several clients available for Android, like e.g. aNag and uNagi Nagios client on android (the latter even has plugins for Locale/Tasker for more flexibility: Locale uNagi Notifier Plug-in and Locale uNagi Settings Plug-in, so you even can setup automatic actions on your device based on the notifications).
Plenty more of similar solutions available, e.g. with Cacti...
The simplicistic approach
At the end of your scripts, you could place a line to have them send you a mail to e.g. your GMail address. This can e.g. be done using the
mailx -s "[WooFoo] script finished" firstname.lastname@example.org
(of course, replace
email@example.com with your real address). As soon as that mail arrives, GMail (or any other mail client you use on your Android device) would trigger a notification.
Enhancing the simple approach
Tasker can react on incoming mail for the GMail app or K-9 Mail. That's why I put the