I saw an email the other day stating that we all have at least one burglar alarm for overnight.
Just keep the keys to your car on your bedside nightstand. If you hear a noise, hit your emergency alarm on your car remote. Your car will honk and flash it lights for a long time. This should certainly be enough deterent if there is an intruder or someone trying to break in.
Of course it would help if you would park your car at least in your driveway...but it would be better if you cleaned out your garage and parked it inside so it doesn't get broken into instead.
Hope you fined this helpful for that is how it is intended.