One way is to use Astroberry on a RPi as it has a relay driver the uses the GPIO pins. There is also the indi-rpi-gpio driver which is similar and also allow PWM on the GPIO pins and can be installed on other RPI systems like StellarMate. The RPi can be controlled via Wifi.
I'm sure there are a multitude of "standards" for wifi enabled devices. As we used to say "the great thing about standards is there are so many to choose from!". As long as there is an API for the device then a driver could be written but the RPi approach can drive conventional relays and the drivers are already there.