Here is a motor driven pet door that is activated by a MS-4 ultrasonic collar, allowing you to let your pet in without you having to open the door manually. It uses a directional sensing system to open the door when your pet is approaching and not when it is sleeping next to the door. You can select from In Only, Out Only, Full Access or Closed & Locked access controls for your pet.
The door is wind and weatherproof with airtight seal. It also offers automatic deadbolt locking. You can get it for $349.99.