For those of us who love technology and who have just a little geek in us the DoorBell Fon is right up our alley.
When a visitor presses the button on the door intercom, the DoorBell Fon rings the phones in your home with a distinctive ring. Pick up the phone to converse with the person at the door. If you are on the phone when a visitor arrives a call waiting tone will sound to alert you. In fact, the DoorBell Fon system will even work without phone service. The system provides the necessary voltage to operate on its own.
Up to 2 intercom stations can be attached. Add the optional lock controller and an electric door strike and you can unlock the door from the phone by pressing "*". Easy 2 wire connection to door intercoms. Works with answering machines, most home PBX phone systems, and phone-company provided services like voice mail. Includes one door intercom station, which measures 3 7/8" X 5 1/8" X 1", and a power supply. A Brass Outdoor Intercom Station is also available.
Normally, after someone presses the button on the outdoor intercom station, the phone will ring and there will be approximately 20 seconds available for you to pick up the telephone and be automatically connected to the doorbox. By installing an add-on chip, you can add a total of 8 rings or about one minute.
This item is rather expensive, but man is it cool! Click this link to purchase or view installation instructions for the DoorBell Fon from smarthome.com: http://www.smarthome.com/5070.html.