Taransay RF module.
Design files hosted on GitHub.
A long time ago I used sensors from the OpenEnergyMonitor project to sense temperature, humidity and electricity usage in my house and my parents' cottage. I had a few annoyances with these boards so around 2017 I decided to make a new design, removing the bits I didn't want and adding new features. There have been a few iterations to this design but I seem to have settled on the current design which is a module that either sits on its own or plugs into a larger circuit to provide it with a microcontroller and wireless capabilities.
A wireless "hub" is also needed to pipe data to a web server running Home Assistant. My hub is a Raspberry Pi running some custom Python code to provide a bridge to the outside world, using asyncio to keep delays to a minimum. This software is still in a bit of flux so I've not published it yet. Previously I used emoncms but it's become a bit too focused on OpenEnergyMonitor hardware to be really useful for my custom boards, and I'm also not a fan of their data payload format.
The range of these boards is spectacular: typically over 100 m, capable of penetrating through many thick walls. This is thanks to the use of HopeRF RFM69 modules.
Battery consumption is also minimal: for most sensing applications, sleep between measurements allows for microwatts of power drain, allowing for battery lives of years, which I've verified by running such nodes at the cottage.