High Tech Pet Power Pet Electronic Pet Door
If you are looking for a motor-driven option, then the High Tech Electronic Door is a good choice. As a high tech electronic door, it is activated by the MS-4 ultrasonic dog or cat collar. The door then slides vertically for entry or exit.
The door and collar use a directional sensing mechanism. It then only opens when the pet directly approaches the door. When the pet is sleeping next to the door or wandering by it, it does not open.