To keep things simple, we will just be building something that can take care of a single plant. This will provide us with the most flexibility in terms of placement, as we would just have a single system next to each plant, no matter whether it's on a windowsill, table, or terrace somewhere.
In addition to measuring the soil moisture level, we would also want to be able to have the system automatically water the plant at set trigger levels and for us to be able to monitor this process. This requires some kind of network access, preferably wireless so that we don't have to run any more cables than the power connector.
This makes the ESP8266 MCU very attractive, with the NodeMCU development board an attractive target for developing and debugging the system. We'd hook up a soil moisture sensor to it, along with a peristaltic pump.
By connecting to the ESP8266 system's IP address using a web browser, we would see the current status of the system, with the soil humidity level and optionally...