A friend of mine was a Philadelphia police officer for 25 years or so. He said that by far the two most effective anti-break in measures are motion sensors on outside lights and a dog.

Lights that turn on as one walks around will spook most intruders. Any dog that barks, even a very small dog will also scare away most intruders.

That is what he told me anyhow. I don't if it is true or not. Just passing it on...