If you have a feline friend at home, you know exactly what it's like. Every now and then your cat will happen to jump onto your keyboard (as if not on purpose!). If your Mac is turned on and you have some documents open this can be particularly annoying. You can have your Mac automatically lock or use CatNip for a more playful way of protecting your Mac from your cat.
You can set different alerts on CatNip: a beep, a display message or have the desktop fade out. Also make sure you adjust the sensitivity, so that CatNip does actually activate itself when your cat pounces on your keyboard. So CatNip only offers limited features, but at least it gives you a choice of three different alerts.
CatNip is an application for Mac OS X which can alert you and block your Mac, when your cat jumps on the keyboard.