I got into home automation because I wanted to control the temperature in my office using a plug-in electric heater and a temperature sensor. I set up a thermostat in Home Assistant that would turn on the heater when the room was cold, and turned it off once it reached the desired temperature. Then I put it on a schedule and set up some automations, so that my office would be warm by the time I got up, and the heater would turn off if I was away from home.

After that, it turned into a fun hobby. There's some cool things you can do with it, but it's just a lot of fun to write programs for my house and figure out routines and automations.

All our lights turn on automatically via motion sensors, and stay on based on bluetooth presence detection using our phones and watches. I also have a "night mode" that uses a lower brightness, and switches to using night lights in our hallway and bathrooms.

When we get up in the morning, the coffee machine turns on, the kettle starts boiling, the blinds are opened, and the TV turns on and plays a breakfast news program. (If we get up later then it chooses the TV channel on a 1 hour delay.) I set up a "movie mode" for our living room that turns off all the lights when a movie starts playing on our Roku, and turns on some dim lights when the movie is paused or stopped. We also never need to manually turn off the TV or stereo. When my wife and I both leave the living room and go downstairs, then everything turns off automatically after a few minutes (TV, stereo, any podcasts playing on an Echo, etc.)

When I walk into my office, the lights turn on, my computer wakes up, and it automatically unlocks when I'm wearing my Apple Watch. If I'm away from my office for a few minutes then the screen is locked, the lights turn off, and Spotify is paused. (Then Spotify resumes playing when I come back in, if it was previously paused by an automation.) Whenever my webcam turns on for a Zoom call, my air purifier is switched to quiet mode, and it turns off the fan in the bathroom near my office. It also turns on a ring light for better lighting, and turns it off when the call is finished.

The automations for our alarm system are really useful. Our alarm is automatically armed in "home mode" at night, and "away mode" whenever we are both away from home. It's automatically disarmed in the morning, and when we arrive home.

Our kitchen rangehood extractor fan turns on automatically when we're cooking, or if the pm25 in the kitchen goes above a certain level. Home Assistant also controls all of the heat pumps in our house, and all of our plug-in electric heaters are controlled with a thermostat that uses temp/humidity sensors.

I'm not quite finished yet - I don't have any cameras, and I want to put Amazon Kindle Fire tablets around the house to use as dashboards / controllers. It's also been surprisingly difficult to automatically open the garage door when we arrive home in the car, so I'm planning to use some ESP32s and design a secure protocol using 433 MHz transmitters/receivers. (I wasn't able to get presence detection working reliably with WiFi, even with a long-range antenna.)

Anyway, it's a hobby with lots of fun puzzles and challenges, similar to designing a Rube Goldberg machine or building a model train set. It's nothing life-changing or super important, just something fun to work on.