I've been robbed before while not at home and lived in a neighborhood with a LOT of crime and gunshots. Still, I just left the door unlocked nearly 24/7. I'd rather they didn't break my door and let the weather in. My ex, wife at the time, got a Chihuahua. They are the best alarm systems in the world, as long as you're defending against everything, including blowing leaves or a plastic bag in the wind or someone down the street....
Drug lords in Mexico use them in packs as alarms. They're also referred to as desert piranha. Look it up