Once a month the Con Edison man comes to my building, buzzes every apartment, and enters each in turn to read the gas meters. It's a pain in the neck because I have to leash my intruder-unfriendly dogs and hold them at bay while he enters.
In the San Francisco neighborhood of Bernal Heights, the houses have this feature that obviates the need for the gas man to enter the house, or even ring your buzzer:
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Now that's smart.