From Google's Graveyard
At Google I/O 2011, Google released an API named "Accessory Development Kit" with much fanfare, accompanied by Arduino Mega ADK. A lot of people, HCC developers included, were very excited because this offered a gateway into the physical world, reinforced with the promise of seamless application deployment, the missing part for most Open Source Projects.
Then it released ADK 2012 a year later, backward incompatible with ADK 1.0.
Then... nothing. The promise never materialized. Google didn't say a peep, original ADK documentation references now hit 404 pages, and even the original ADK URL sheepishly avoids the very "ADK" term.
So even though the whole Home Climate Control ecosystem at some point was running on Android, the whole effort was wasted because ADK was effectively abandoned by Google and never picked up by anyone else.
Still, it was a valuable learning experience that allowed the ecosystem to evolve into what it is today.
Rest in peace, ADK.