In real life, “open mike” terminals are becoming popular, that listen for commands addressed to them and answer questions, perform online actions, or operate compatible smart-home controllers or an ever growing number of IoT devices. In ten years (when my story is set) they may even work as well as they do in the commercials.
But what's a totally different way to perform generic or pre-scripted commands in the home? It doesn't have to be a full language, just handle things like adjusting the lights, setting “modes” (group presets for any number of devices), make the temperature warmer or cooler, and other ubiquitous things in a home. One universal command can be to “listen!” so then you can talk to it, for more complex things.
I envision a lavish home where the characters control the lighting while moving from area to area without having to go to light switches; just automatically do it without breaking stride. It also controls temperature in a shower, operates window blinds, and such.
I recall in on of Asimov’s robot novels he describes controlling things with hand gestures. I don’t know if that’s great, though — how does it monitor your hands?
What other ways might one command a smart home or specific stations therein?