Viessmann is planning to publish the Viessmann / vitoconnect open API in the year 2020.
It has been announced in the Viessmann Community
They are searching Test-User.
If someone is interested, it is necessary to be registered in the community and to contact Christoph_Meyer from the Viessmann-team.
Next Viessmann send contact-mails to the interested community-members with further details.
Thank you for notify me. I have just ask to be added as test-user. Tbh, I was thinking of adding a Rest interface in front of my php code because low level api is too thight to the language. If Viessmann expose it’s own Rest API and that this one is simple enough, I’m not sure to see the interest to keep developping my API. If they provide an OpenAPI specs then my api would only be interesting as “Oauth+OpenId client” without wrapping the current viessmann api.
That page is active for some time now, but logging in order to get detailed info is not ( at least to my knowledge, tested 2 minutes ago). Status unchanged : only intentions posted by Viessmann.