Having a UMIK-1 measurement microphone for use with REW (or similar) has been really great for my year. I'm building a recording studio at home, and having the quick ability to capture and measure data about my room over time has been fantastic. I've also used it to measure the volume of some things, and profile why a few of the rooms in my house were too echoey which led to remediation techniques.

https://www.minidsp.com/products/acoustic-measurement/umik-1

I also got a FLIR infrared camera, which was a little bit more than $200 - but there are cheaper models that would have done the trick just as well realistically. My home was built 140 years ago, and some ability to inspect heat-creating things through walls has been useful.

Another really useful one in this price range was a Logitech MX ERGO trackball. I like how it requires less space and solid surface than any mouse. I also like the angle it puts my hand at. Multiple device support is good.