With respect to Unity, you can look at the following list of integration tools related to Google Cloud products.
If you are not willing to purchase them or want to come up with your own solution, you can make API calls to the desired Google Cloud services.
Its is also possible to use C# client libraries for Google Cloud Video Intelligence, Google Cloud Vision, Google Cloud Natural Language, Google Cloud Speech-to-Text (there is no C# client library for Google Cloud Text-to-Speech yet, therefore API calls are the only option right now).
solved Google cloud platform for unity games