A Nest Learning Thermostat is a fairly well-developed participant in the Internet of Things. It connects to your home wi-fi network and the internet through it. There are apps for you to interact with it remotely, so as you return from your vacation, you can turn the furnace back up (or your a/c down) to a more comfortable zone. If you forget to set your heating to reflect an extended empty house, the Auto Away feature will hopefully notice for you. It "learns" your typical usage, so rather than programming it to warm the house up around the time you wake up and cool it down as you head off to bed, it knows to do that for you after you have been setting it that way for a while.
We have two furnaces, two air conditioners, and three zones. The downstairs furnace and a/c are one zone, and the upstairs furnace and a/c cover two zones, each with its own programmable thermostat. The Nest replaced the downstairs thermostat. R. had programmed the programmable thermostat, and we are quite diligent about setting the temp low in winter when when leave on a trip and high in summer likewise. It is not clear whether the Nest will be an improvement from an energy use perspective, given the preceding use of programmable thermostats.
What I am hoping is that I will interact with the thermostat less. I modify the settings manually often enough that the Nest might do a little better than the program. I'm not sure tho; perhaps I am not predictable.
Some utilities offer a rebate on your Nest -- $100 on a $275 gadget, so definitely worth looking into.