Buy a cat. In my area most people are dog people and it's been my experience that dog people are VEHEMENTLY dog people. The mere presence of a feline in your house will send them into fits.

Ergo:

The chances that a potential burglar is a dog person of this type is very high and thus having a cat will dissuade them from entry.

or to put it another way:

Minecraft has taught me that Creepers hate Cats.