Update 1 (Jan 24): We got some reports from people that they are still able to create accounts and generate the right keys. We just verified and this is the case. So for now you can still access your data, which is good. We’re still puzzled on the response to our tweet. And thanks to Reddit user /u/lefos123 for pointing out that they announced this on Nov 2018.
Although it’s still working, we’re still scared about the future of the Nest API.
Some sad news for users with a Nest product: Nest is no longer accepting new developer accounts. This means that if you bought a Nest thermostat, you are no longer able to access YOUR data.
New Home Assistant users will not be able to integrate their Nest products. Home Assistant users that have already integrated Home Assistant with Nest are not affected.
We hope that Nest will implement a new program or add support for locally controlling the Nest thermostat, if they do, we will update this post. Until then, we can no longer recommend buying or using any Nest product.
We're currently restructuring our developer program and are no longer accepting new developers to the program or performing client integration reviews for existing developers until the new program is implemented. Stay tuned for further details and announcements.
— Nest (@nest) January 16, 2019</blockquote>