You surely do not know who is standing in front of your door. However, this problem can be solved by installing a driveway alarm system. The main aim of these systems is to alert the owner whenever someone enters the property (before they get to the front door). The alert is given in the form of chime. When you have this system installed in your commercial or residential area you know you are in safe hands. Apart from this, it can also detect the movement of the people, walking, vehicles, and also large animals. If you want to buy them it is wise that you have it purchased from a reliable source. They are worth every penny!
Website - http://www.drivewayalarmproducts.com/