Any; from my experience developing voice UIs using Google products and APIs I figured it was a very good thing to segregate the application logic from its integration with select platform(s) like Google Actions, Alexa skill, Android Things, a standalone device, or one of many 3rd party chat application like Facebook Messenger or Hangouts Chat...

There are so many options it seems like the right thing to do is to release on those your potential users have access to.