Dogs are great deterrents to burglars. Even a small, noisy dog can be very effective. Burglars do not like to have attention drawn to their presence, or the obstacle of a dog bothering them once inside. A well trained dog can be a wonderful asset. Barking at a ringing door bell may seem like an annoyance, but to a would be burglar, it is a warning. Even showing your control over a well trained dog in public can intimidate someone with bad intentions. They have to assume that if that dog will sit and stay when you tell it, it will also attack them or defend you when told.
If dog's are not your thing, consider an electronic version. There are several options out there for this. Basically a recording of a dog barking that can play based off of a motion detector or even a switch (like a doorbell) These work great in garages because the sound will often echo and seem larger than it really is.