I actually modified the Ecobee connect app and created a Nest (connect) app that uses the official Nest Api. It about 60% complete all that needs to be finished is the methods that handle the device data updates and tweak the device type.
It will work like all of the other Connect type apps: it authenticates, detects, creates, and polls the nest service for data and updates the Thermostats and Protects.
I just stopped working on it about a month ago when I kept seeing little clues in the ST Github repo and images of the Nest thermostat in the some examples in the ST Documentation and figured why bother .
If there is enough interest I would think about putting it up on github so someone can collaborate with me to complete it.
It would be great to complete the work you started to have a nice Nest integration. It doesn’t sound like ST and Nest and going to come together on their own anytime soon.
Please keep me posted should you decide to do this.