Indoor/outdoor temp sensors. Anything that needs a cheap temp sensor. Really handy since they just steal power from the bus (parasitic) so you don't need to run extra wires for power.

For me, I was using them as environmental sensors for an aquaponic setup (water more often when it’s hotter)

I put together some low effort esp8266 temperature/humidity probes. I used DHT chips cause they were cheaper/bundled with a board, but the tutorials said the DS chips were better.

I have several for homebrewing - monitoring mash, sparge, and fermentation temps.

I have a bunch for a related process. I don’t need them to be super accurate but they should be consistent and repeatable and the ones i have definitely are that.

I just bought a bunch of cheap indoor/outdoor weather sensors, I'd imagine they might apply.

May I ask what you bought? I've been looking for something like this but everything I've found has been pricey.

Ecowitt everything. They whitebox for Ambientweather and others, there's a whole rundown on wxforum:

https://www.wxforum.net/index.php?board=111.0

I never knew about wxforum. Awesome. Thank you!

I use a waterproofed version as a water temperature sensor (in the lake).