I made a similar setup with Home Assistant running on a low power Raspberry Pi 3A+ connected to a Xiaomi Mijia Bluetooth Low Energy temperature and humidity sensor (model code LYWSDCGQ). It takes a single AAA battery and it's lasted almost a year on one.

There's a ready-made Home Assistant component but I wrote up a guide on how to read the data from a Linux terminal on your laptop: https://unop.uk/xiaomi-mijia-bluetooth-temperature-and-humid...

I also have Volatile Organic Compounds / equivalent carbon dioxide (Sensirion SGP30) and Particulate Matter (Plantower PMS5003) sensors soldered up to a Raspberry Pi Zero W over I2C/UART for logging. It lasts quite a while on a USB battery so you can take it out and about. An ESP8266/ESP8285 would last longer but it's easy to log with a python script and the SD card gives you loads of storage. I haven't written this up yet but will if anyone is interested?