This is an WIFI-based appliance module using the ESP8266 (ESP12) and a latching relay. The appliance module is powered from the AC line using an inexpensive 5V 1AMP universal input power supply which is attached to the board. There are provisions for local control using a pushbutton switch, and there is an option for a WIFI status LED. The firmware is written in C and the appliance module is controlled using MQTT and JSON.
WIFI based appliance module using the ESP8266 and a latching relay – [Link]