Your average smart phone knows where it is, the exact position in 3D space, what devices are nearby, whether it is being held versus on a table or in a pocket, whether you are laying down, sitting, walking, jogging, running, biking or driving, whether you are indoors or outdoors, what the temperature is, what the atmospheric pressure is, what the relative humidity is, UV levels, air quality levels, the tone of your voice to determine whether you are happy, sad, angry, ..., and in many cases what your heart rate is when using it by looking at your face.
And more sensors are being added with each revision to make them better able to be everything for you.
There are even sensors out now that will build live 3D models of whatever the phone sees, letting it know what is in it's surroundings.
Your phone already knows the things that your thermostat *can* know, except it does a better job because in our hyper-connected, instant gratification culture it has become the 8th deadly sin to be anywhere without your cell phone for 5 minutes.
While it is good to be considerate about what could happen should all of these existing systems that we already have in our homes and are adding daily get linked together into one gigantic monitoring system, it is an exercise in futility considering that we knowingly don't care because next year we can play Kinectimals on our phone and have our ePet interact with the world by jumping up on the couch or hiding behind the counter.