There are no smart plugs at this time that can be added directly to Ring. I assume in the future we may see some Z-Wave devices.
There are 3rd party integrations today with Smartthings and Homebridge. But careful as they may require you to supply your Ring account credentials to their configurations (some are even added to plain text files) in order to talk to Ring. Maybe in the future we may see API integrations instead.
Alexa can turn on your Ring alarm and you can even use Alexa Guard, which can randomly turn on/off lights to similate a living environment.