Tell your spouse, your children, your neighbors, your parents, your Dr's office staff, the check-out girl at the market, everyone you run across about this solution...
Put your car keys beside your bed at night. If you hear a noise outside your home or someone trying to get in your house, just press the panic button for your car. The car's alarm will sound, and the horn will continue to sound until either you turn it off or the car battery runs down.
I'm told this tip came from a neighborhood watch coordinator. Next time you come home for the night and you start to put your keys away, think of this:
It's a security alarm system that you probably already have and requires no installation. Test it. It will go off from most anywhere inside your house and will keep honking until your battery runs down or until you reset it with the button on your remote. It works if you park in your driveway or garage.
If your car alarm goes off when someone is trying to break into your house, odds are the criminal won't stick around... After a few seconds all the neighbors will be looking out their windows to see who is out there and sure enough the criminal won't hang around for an introduction.
Also, remember to carry your keys in hand while walking to your car in a parking lot. The alarm can work the same way there ... This is something that should really be shared with everyone you know and/or value.
P.S. I am sending this to my friends because I think it is an inexpensive way to address a potential problem. This solution could also be useful for any emergency such as a heart attack where you can't reach a phone.