Wireless Module for Capacitive Soil Moisture Sensor v1.2.
Running on cr2450 battery (500mA).
Used the MySensors library
Operating mode - 8 mA Sleep mode - 2.2 microamperes
GitHub - https://github.com/smartboxchannel/EFEKTA_E73B_PWS_MODULE (links, gerber, cod, bom, foto)
Cost of the assembled device - $12
Video: