Given all the air quality issues in CA right now, I've been planning to put together an air quality + temp + humidity sensor that I can run off a battery and connect to my wifi. I already bought the sensors which I have connected to a Raspberry Pi just to play around with them, but of course a RPi won't last long on a battery. I really want something I can just toss in the corner of a room and easily move around.

I've mostly been looking at the ESP32, though (newer, also has bluetooth and 2 cores, and is lower power), and some of the ARM Cortex-M-based microcontrollers.