There is no other API to switch to, as Google controls the protocol, no open standard exists to replicate the Nest API server, and Nest devices don’t support targeting a self hosted API.
If you as a user or third party provider integrated with this API and rely on it for functionality, you have no alternative nor recourse.
Isn't "Works with Google Assistant" supposed to become the replacement API? It seems like they don't offer direct access to the data or the device but plan to allow "some" level of control?
(I don't know the space, apologize if my questions are naive...)
> As a Works with Nest developer and partner, you will not be able to access or control Nest devices once the Works with Nest APIs are turned off on August 31, 2019. Moving forward, our team will focus on making Works with Google Assistant the most helpful and intelligent ecosystem for the home, enabling all of the products in your users’ homes to work together.
We encourage all smart home developers to visit the Actions on Google Smart Home developer site to learn how to integrate your devices or services with the Google Assistant.
If you as a user or third party provider integrated with this API and rely on it for functionality, you have no alternative nor recourse.