This is likely extremely naive: But would requiring a patent-filer to demonstrate a working implementation help mitigate this sort of thing? From what I can tell, Honeywell at least had the foresight to know where the tech was heading, but seemingly exerted no actual effort in getting there. Maybe I'm wrong about that - but this pattern seems to be true for patent trolls, at least.

If that's the case, they're basically building an artificial moat. So what now? Does Honeywell sue Nest out of existence? Require Nest license their patent? What are some likely goals and motives? What happens now?

There's a big difference between saying we WANT to go the moon, versus we WENT to the moon, or even we CAN go to the moon.