Evil RFID technology is already used in doorways at stores, in order to beep angrily at customers who are trying to redistribute wealth, as well as at unwitting characters with lawfully purchased goods that have not been properly de-RFIDed. Not quite so Evil RFID techhnology allows implants to be left in various animals for decades.

I propose that we develop a new RFID tag, which can be installed in a key cover, such as those on car keys. A sensor can then easily be set into the door of the home.

The RFID can then detect when someone is leaving the hosue without the key, and beep angrily at them... much like how my car beeps angrily at me when the passenger door is opened while the car is running, lest I should clamber over the seats, leave, and lock myself out of the car with the engine still running.

The door could be equipped with powered locks, which it would not lock unless the homeowner left with a key, or it might be equipped to use them only after a set amount of time, after which it might be able to send a call, page, or other communication to yourself, or a neighbor who has been entrusted with a key.

Certain refinements could be made to prevent unnecessary beeping. The homeowner might get an implanted RFID device (also known as "THE MARK OF THE BEAST"), so the door knows when it is the homeowner leaving, rather than a guest showing themselves out... Or the door might be made as a double cylinder lock, and would only beep when the key was not in one side or the other... Or the homeowner could keep a key at all times, and see the guests away personally. The door would then sense the key, and not get all uppity.