We have an Echo Dot that has Alexa, and all we have used it for so far is to play music through the stereo. My daughter has one of the Nest thermostats and she loves it !
We went to visit her on Christmas Day, and she was showing us how it works. When she walks past, it “recognizes” her and lights up, so if she is gone and comes back, the thermostat will turn the heat up if it has been lowered while she was gone. It also changes according to her schedule, so lower temps when she is gone to work, and when she is sleeping at night, and then warms the house up when she comes home.
I really like the idea of programmable home equipment like this, and we will probably add some of the smart plug-in receptacles so that we can turn some lights on and off of we need to do that.
I can see that an extended power outage might cause problems; but that kind of thing is going to cause some kinds of problems regardless, and it would be really nice to have a warm house and lights on if we happened to go somewhere and get home later than we expected to.