"Is Nest, like Hal, also watching what you do? You bet. I found this on their privacy page:
“We collect data from several sensors built into the Nest Learning Thermostat. These sensors register things like the current temperature, humidity, and ambient light in the room. They can also sense whether something in the room is moving. We also store PII about your use of the product, including sensor data and your inputs from mobile and other devices on our cloud servers.” PII is the abbreviation of personally identifiable information.
So, while Nest is managing the temperature, it is also keeping tabs of your movement and collecting various other bits of information about your home and sends that back to a central server."