Electronic pet door
Those pet doors with flaps might save you from getting off the couch to let Max into the yard, but they also spew hot air from your home. Plexidor Electronic, an electronic pet door from Pet Door USA, provides increased efficiency and security for your home. Pets wear a "collar key" to trigger the door (much like your key card lets you in the parking garage), which has a panel that panel slides up just long enough to let your furry friend in or out.
The collar key uses RFID chip technology, takes no batteries, and is waterproof. The door is made from the same material as football helmets, ensuring your home's security. Doors range from $129 to $800.