All it requires is a moisture sensor, a water pump, and some sort of container to hold a reserve. When the soil gets too dry, the moisture sensor will signal the pump that it's time to re-hydrate.

It runs on an Arduino MEGA 2560 PRO (or similar microcontroller) and supports a wide array of additional hardware including pressure transducer, water level sensor, flow meter, OLED display, and more.

I've just come across a no-name non-contact, high-precision 80 GHz mmWave radar sensor for liquid level detection with a 40m ...