Flex TV. is a web application that interfaces between google Assistant and Plex to allow you to control playback of media using Actions for Google or IFTTT.
Additionally, it interfaces with the API's for Sonarr, Radarr, Couchpotato, Sickbeard, and Sickrage.
It also has customizeable webhooks, so you can basically control anything that has an open API with your voice. If you can send data to a URL to do a thing, you can program it in Flex TV.
Interested? Check out the Wiki to get started.
Don't feel like setting up a webserver? No worries - I'm hosting Flex TV as a service here: https://app.phlexchat.com
You'll also need the Cast plugin installed:
https://github.com/d8ahazard/Cast.bundle
And here, have some pretty pictures: