7 years ago we had a breakin at 5am on a weekday. According to the guards, the modis was that they climbed over each back garden wall in the street, banged on a window of each house, continuing onwards to the next house. If an alarm went off or a dog barked, they just continued, if there was no deterrant, they came back, snapped the patio door lock, came in and take whatever was handy. In my own case, I disturbed them and got a smack for my trouble. They took the car keys, but left them in the garden, probarbly did not like my car!
As a result, we moved house. Subsequently, we have gates with a post behind them, anti snap cylinders on all the doors, and the alarm goes on everynight.
My wife got one company to do the lot. We have not been broken into since, while other houses in our area have.
I think an alarm box that give off a neon flasher indicating that its on along with a high visibility parking post should be enough to deter any one.