Basically the author uses an ESP8266 with a 433 transmitter to control them. The ESP listens on the network for what to do and then after you sniff the traffic for the 433, turns the correct switch on and off. Pretty cheap solution to give you WEMO like switch control. Figure around $10 for the controller. Another $20 for 4-5 of the wall switch outlets.
http://www.makeuseof.com/tag/control-cheap-rf-power-sockets-openhab/