While groovy works this is smartapp that I run and use. At the rate edge drivers beta is going, it might work for a long time.
It works well and can be activated and deactivated with automations.
you can choose several switches or lights that you have installed.
This link has all the institutions on how to install and use
If you want to use new edge drivers with some switch, plug or bulbs, you can install any of these drivers on your devices.
Zigbee switch Mc
Zigbee switch power Mc
Zigbee light multifunction Mc
These drivers have random on and off functions, which can be programmed with a maximum and minimum time individually and activated and deactivated in groups with automations. Each will perform its own random on-off-on cycle.