Selfhosted

You can use it for the most basic of things and build from there. My first automation was turning off all the lights around my home at bed time (triggered by a button which makes it less automation and more remote control I guess). From there the bug bit me and I do all kinds of crazy stuff now.

The most practical is my load-shifting power automations. My power company has a rate plan that rewards you with really cheap power if most of the time in exchange for not using power during peak times. I selected this plan and automate a near-complete shutdown of the electrical systems in my home during peak times - the A/C goes off, the water heater goes off, the pool pump off, nearly everything except for lights. Total house power use during this time goes to like 400watts as a result. It has saved me hundreds on my power bill, even with adding an electric car that needs to charge every night!

The most magical is likely the automations around my bed. Both going to bed and getting out of bed are detected and magical stuff happens. When the first person gets into bed (either my wife or myself) almost nothing happens other than the lights dimming in the bedroom to get ready for sleep. Once the second person is in bed a bunch of things happen - all of the lights in the house go off, the doors lock (if they weren't already), the garage doors close (if they weren't already), the security system arms for "Home mode", the HVAC systems go into eco mode outside of the sleeping areas, and a toggle is set for "Sleep mode" that allows me to have other automations make decisions based on it (like if an interior motion sensor turns on a light during sleep mode, the light is turned on at a low dim mode). When the first person gets out of bed after our wake up time of 06:00 the coffee maker will start brewing. Once the second person is out of bed the sleep mode is disabled and most of the home systems return to normal.

Another favorite is the nightlight mode for my kids. Their bedrooms are on opposite ends of a hallway with a shared bathroom in the middle. During sleep mode, if one of them opens their door at night, the lights on their side of the hallway will turn on to a very warm color and very dim, but plenty to walk by. The bathroom lights also turn on dimly and everything automatically turns off a few minutes after motion stops being detected.

I've got tons of stuff related to motion detection for security and such too. It's really a sickness once you get into it. I can't stop sometimes... send help...