LinkNode R4 is a WiFi relay controller and it is powered by ESP-12f ESP8266 WiFi module which is compatible with Arduino programming. There are 4 relay channels and each channel allows you to control high-power devices (up to 10 A) via the on-board relay. LinkNode R4 can be used to remotely turn lights, fans and other devices on/off. The WiFi interface will allow you to associate the board with your existing WiFi network and send the commands over the network.
Here's a great DIY Home Automation walkthrough you can achieve using the LinkNode R4: http://www.instructables.com/id/DIY-Home-Automation-With-ESP8266-Linknode-R4-and-A/