Code
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.
Specto is unmaintained. See details here: http://jeff.ecchi.ca/blog/2013/03/21/a-programs-obsolescence/
For users upgrading from Specto 0.2.x to 0.3.x: use File > Import watches to import your old watches from ~/.specto/ (the directory and format has changed).