A FLOSS for GNU/Linux would be Specto.
Specto is a desktop application that will watch configurable events (such as website updates, emails, file and folder changes, system processes, etc) and then trigger notifications.
For example, Specto can watch a website for updates (or a syndication feed, or an image, etc), and notify you when there is activity (otherwise, Specto will just stay out of the way). This changes the way you work, because you can be informed of events instead of having to look out for them. Better than clicking the refresh button on Caturdays, huh?