There are times when my husband has been on business or away for the night when I wish I had an alarm system, just for an extra sense of security.  My mother-in-law received an email with this idea and I thought it was worth sharing if you do not have an alarm system in your house.  Put your keys on your bedside table before going to sleep. If it so happened that it sounded as though an intruder was breaking in, push the panic button on your car key and s/he will most likely decide to turn around.  May be a good idea for some who don't sleep well alone in the house!