RE: Nest thermostats (driver here)
I think what @N4IRS said is right.. the only important thing with setting up the Nest driver on HE is that you get it to show up and work in HE. If it works on HE - just make sure it's checked in the MakerAPI device list and it'll show up in any application which uses the MakerAPI.
I will say setting up the Nest driver was pretty complex.. not sure if it's on par with rooting a Fire tablet but not far from it 
But, so far the driver has been great and now that I have my Nest thermostats displayed in the app, I'll be motivated to support more thermostat features!
I created an account specifically for the dashboard. The devices use a separate account.
EDIT: I also use a different Google account on my wall mounted tablets.. no reason to use your primary Google Account on these
