[tylerlh]

At the end of the day, something has to be wired to the A/C to provide control and the majority of houses today are already equipped with that wiring inside the home (usually into a wall). I don't think there's any rule that says you have to have this in a wall, but I'd be willing to bet most people will prefer having that fancy smart thermostat mounted in the same place the old one was (myself included).

If nothing else, I think it creates a sense of security in that they'll be able to still use it if they lose their controller or their phone dies.

[joezydeco]

But I like jbob's idea.

You can cut a huge chunk of the cost out of the Nest if you drop the LCD, touchscreen glass, and fancy stainless steel housing.

It could be a simple plastic box with the CPU, radio, sensor and control relays inside, and then a hidden mechanical thermostat knob/control to use as a floor + emergency override if the internet cuts out or the phone goes away.

[jbob2000]

That's what I was getting at! (in an admittedly crass way). Split the device between temperature sensing and temperature control.

[joezydeco]

That said, there are devices that come extremely close to this, like the RadioThermostat CT-50. It has it's own HTTP API so you technically could operate it on your own.