The Infrared Cat Door. $94.99. Old pet tech updated for the new millennia? Or something. Cat hackers unite, you have nothing to lose except your free lunches.

 Your cat’s collar key transmits a digital coded infrared signal, which is decoded when the key comes within range of your pet door (approximately 6 inches), permitting only pets with keys of the same code to enter the house. The door re-latches automatically after the length of time you determine. Additional keys are available to be purchased separately if you have more than one cat.