our hackerspace uses a ton of 'sonoff' products from itead ; https://www.itead.cc/sonoff-wifi-wireless-switch.html its a simple and cheap esp8266 based board you can run anything you want on. i -think- it comes with some firmware natively, but i've never bothered to look at it :P
the firmware we flash on them allows them to be controlled over MQTT which works nice for our domotica setup, but i've also flashed one with art-net software once. some manual attempt is at https://nurdspace.nl/SonOff
many ways to apply this ;)