Slightly tangentially related, for those of us who are into gardening and coding, there is a plant monitor made by Xiaomi called Xiaomi Flower Care that will monitor moisture, light, temperature, and soil fertility. It works over Bluetooth and can be purchased on Amazon for as low as $8 per probe but the vendors will often charge around $25. You see a lot of rebranded ones but they're all the same from Xiaomi. It works with their iOS (and presumably Android) app. Someone has released a SDK for it:

https://github.com/vrachieru/xiaomi-flower-care-api

My plan is to use that and build a Raspberry Pi to monitor my plants. And later on maybe control the watering system.

Anyways, it's a nice cheap plant monitoring option. It was really helpful when I was trying to figure out why my plants were turning yellow. People were mostly telling me that I was either over watering or under watering, etc. Then the probes all told me that my soil has no fertility left so I just added some organic 5-5-5 fertilizers and my plants are doing great again. The nerd in me love checking the data every day but would ideal build a Raspi server to sync and display some graphs some day (using a Prometheus endpoint perhaps?)

If anyone has good advice on how to control a set of water valves using Raspberry Pi, please let me know! I know about GPIO but I would like to have a bus of some sort so I can add more valves in the future if needed. Maybe a USB solenoid?