I have a couple Eve Room air quality monitors[0] and like them. You do need the iOS app to view and export (XLSX format) historical data, but there's no cloud service or anything to sign up for. I charge them about once a month and usually look at the graphs every couple of days so I'll see then when a battery is getting low. The only other "smart" devices I have in my home are some lightbulbs, though, so I don't have any automation set up using the temperature or air quality.

[0] https://www.evehome.com/en-us/eve-room