Monotony
This is a very nice application. It runs completely in the background unless you enable its menubar functionality, which will display a simple icon. Also, the price is right.
The only problem with it is that notifications come and go very quickly. A notification will appear and disapear after about 5 seconds, with no option to keep them around. This can be a problem if you leave your computer when a update appears. Why not integrate this with Mountain Lions Notification Center? This would allow the user to configure their preferences for how alerts should be displayed while still remaining seamless.
Wardo1254 about
Monotony, v1.0.1