So many 'smart home' items are nice toys that only work if they can connect to the manufacturer's servers. With Home Assistant, you can build a home automation and security system that is entirely local if you like. It still takes a bit of work because you have to do your research when choosing new devices to add, but it works.
The voice assistant is adequate and rapidly improving, though the recommended hardware is listen-only - voice response is currently mainly available via a phone app.
Anyway, even if you have nothing to plug into it but have an old computer somewhere, it's worth downloading and playing with. Link it to the phone app and suddenly you have family tracking, common calendars, and a weather app. When my kids were in school, I added an RSS feed parser and had it telling me if buses were cancelled or not before we'd even had breakfast. Now I use it wake me up with a weather report and tell me if it's time to put out the garbage and recycling.
Add in a $20 SDR module and it can check your tire pressure for you, maybe pick up signals from a neighbour's weather station. Then you can start extending it with really inexpensive door sensors. This summer I'm adding a floating sensor to my pool to track the water chemistry and temperature and expecting to save a ton of money scheduling the filter pump (with a $20 smart light switch) to run just long enough during non-peak hours to cycle the water and keep it healthy.
I also route inexpensive cameras through it so I can check them from anywhere I want without having them connect to a server in China or wherever.