Apticron is a great tool, it will automatically e-mail you an alert if you have outstanding packages that need upgrading on a *nix systems. Some useful tips to customise it are shown below.
These variables can be set in /etc/apticron/apticron.conf - The file is well commented. Here are a couple of quick more advanced examples.
Custom e-mail address:
CUSTOM_FROM="Server Updates <email@example.com>"
Custom System Name:
SYSTEM = "example.com"
To test apticron rather than waiting for the cron job to run the following from the terminal: