A bell, buzzer, or chime device mounted on or adjacent to a door's exterior, meant to be rung by a visitor to announce one's presence.
There are, of course, smart speakers (which roughly a quarter of American homes have) and smart thermostats, as well as smart thermometers, smart mattress covers, smart coffee makers, smart doorbells, and even, yes, smart toasters.2018 December 18, Joe Pinsker, “The Coming Commodification of Life at Home”, in The Atlantic, archived from the original on 25 Jan 2019: