My pickup stays in the driveway, and if it's parked facing uphill the alarm goes off when I pull my GTO out of the garage. Never happens if the truck is parked facing downhill. Shock sensor is just a bit too sensitive.
I've had a dozen alarms and sold many more. The bottom line is that the blinking light is simply a deterrent, and will hopefully cause a potential thief to look elsewhere for an easier target. Alarms don't stop bricks, and as the reply above says, the thief would be long gone before you could do anything about it. I like the alarm for the goodies it gets me-remote starter, remote automated windows, radio turn-on, and others. And a LOT more range than the factory key.