Meet the Pebble Smart Doggie Doorbell: a doorbell for your dog with a built-in treat holder. You can train your dog to ring the Doggie Doorbell and communicate with you without scratching or damaging your door. No wiring tools are required. The twin-pack lets you install a transmitter button on each side of the door, so your dog can let you know when it wants to go out or come in.
This wireless bell offers volume control and a range of up to 250 feet. You get 36 selectable tunes. The Twin Pack sets you back $52.