The "Nest" is simply the wrong approach. By itself it is nearly worthless (my not-so-humble opinion) for anyone but the most technologically incompetent thermostat users out there. And even then, you'd have to wonder. Where is the data on how many people can't or don't program their thermostats?

Now, some people might buy it just because it looks cool on the wall, and that's OK.

A real thermal management system for the home does not start with a high-design thermostat on the wall. You need multiple types of sensors in every room and multiple outdoor points.

You need to change the way airflow can be channeled around a home.

You might even need to change the paradigm and heat/cool objects that can provide thermal inertia (like the floor or walls) rather than just air.

You need to be able to selectively inject other heat sources or sinks into the system.

You need solar thermal panels and geothermal heat exchange system in the ground.

As far as control, a very simple embedded PC board running embedded Linux would be the "lazy" way to build it. It would actually be overkill, but there's an argument to be made for the COGS aspect of it.

Any number of relatively low cost embedded boards running very simple embedded software could monitor the sensor array, make decisions and activate valves, fans, etc. as needed.

I guess what I am saying is that you really can't fix the problem without engaging in a fundamental pivot from what we've been doing to thermally manage homes for the last, say, 100 years.

Having said that, it is a lot easier to sell a cool looking $250 gadget than asking someone to spend $5,000 to modify their home. Even though the gadget is very likely to not do much and the more extensive home modification is almost guaranteed to save the home owner thousands of dollars per year.

Talk about an opportunity for government stimulus!