Automatic Locking Pet Sensing Door

This is the patented pet door that automatically unlocks its flap only when a pet with a "smart key" approaches, giving your dog or cat unlimited freedom of passage while prohibiting unwanted animals from gaining entry. The smart key attaches to a pet's collar and transmits a coded signal that activates a spring release in the door, allowing your pet to push through the flap. Approximately 15 seconds after your pet moves beyond range, the door automatically re-locks. $249.95 at Hammacher Schlemmer (via the green head)