if you leave the car outside anyone come brake your car window, open your garage and in our case be inside the house. Just a thought.
I see your point, but if you're worried about that just get the security package. Active security has motion sensors so even if they don't break your window and set off the shock alarm they'll be lighting up the neighborhood. Should be enough to deter someone from going into a house while a car alarm is going off right outside.
If someone's willing to smash you car window to get into your garage they're more likely just to bust your house window or just use a sawzaw and make their own door.
I've actually been thinking about a way to mod my security setup to dial my cell if the alarm is triggered. People these days may ignore a car alarm in a parking lot but i sure as hell will be sprinting out of the store with the largest object not bolted down.