Sonoff is a WiFi wireless switch that can connect to a wide range of home appliances. Out of the box, Sonoff transmits data to a cloud platform through the home WiFi router, which enables users to remotely control the connected appliances, via a mobile application called eWeLink.
Sonoff can also be used with an open source firmware called ESP Easy. ESP Easy allows users to fully configure Sonoff (IP address, DNS, gateways, sensors, rules, etc...) using a web interface. Sonoff with ESP Easy is becoming a very popular device for DIY home automation applications.
A few Sonoff links: