To be extra safe and secure at home at night, especially if you're at home alone, put your car keys beside your bed when you go to sleep, or keep your spare key fob for your car there all the time. If you hear a noise outside your home or someone possibly trying to get in your house, just press the panic button for your car.
The car alarm will be set off, and the horn will continue to sound until either you turn it off or the car battery dies.
This tip came from a neighborhood watch coordinator. Next time you come home for the night and you start to put your keys away on a dresser or kitchen counter or credenza in the hallway, 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 any where inside your house and will keep honking until your battery runs down or until you reset it with the button on the keychain fob. It works if you park in front of the house, in your driveway, or in your garage.