Automation has made its way to everything including a simple item like a pet door. The Power Pet fully automatic pet door accommodates animals up to 100 pounds and is activated by the presence of you cat or dog. Your pet simply wears a sensor on their collar and this activates the door to open, keeping out the strays looking for a nice place to sleep. The digitally coded signal emitted from your pet's ultrasonic transmitter collar not only tells the door how far away your pet is, it tells the pet door in which direction your pet is traveling. This allows it to open only when your pet is on a direct approach, not when it is just wandering by, sitting, or sleeping next to the door. Features include AC or battery power, automatic dead bolt lock, safety retract system, range controls, and hopefully a lower power bill. The door has a tight seal which keeps your internal air from escaping or outside air coming in. The full size Power Pet door runs $349, or a smaller version is available for $299.