Nest makes home integration and control technology, originally for a thermostat. I always found analog, battery thermostats a challenge, never having instructions, never programming them often enough to know how to schedule a week of heating or cooling. This probably wasted a lot of energy. Along comes Nest designing a simple product in the tradition of Apple that replaces your old analog thermostat wire-for wire. As long as you have wireless in the house, you can control the Nest devices via mobile applications. In the year and a half since I installed the Nest our utility bills went way down (to be fair, we also remodeled which installed insulation for the first time).
I was seduced by a neighbor's Nest, but was reluctant to install it due to privacy concerns. (I study Internet privacy issues as new technologies proliferate.) Key to Nest intelligence is the sensors and software that can recognize when you're away from home and automatically reduce usage. So, it can tell when you're away and so can Nest Inc. There is a tradeoff here between convenience and privacy. Still I'm a fan of the device for its simplicity and how it elegantly solved a common problem. And I know management at Nest who insist there is no privacy issue.
Which brings me to the acquisition by Google. Google is a great data aggregator from multiple sources, and analyzes user interests and behavior to provide improved product offering. And the Nest data is potentially one more vector in their analysis. That 's a concern.