> The second advisor, a software developer, immediately recognized the danger of such short-sighted thinking. [...] "A toaster that only makes toast will soon be obsolete. If we don't look to the future, we will have to completely redesign the toaster in just a few years."
My main point was the original poster's idea was probably focusing on the wrong kind of sensor for what he wanted to do. He could still network a bunch of motion sensors.
Also, I'd dispute the idea that my proposals were less "modifiable." If only because they're far easier to implement and a couple of orders of magnitude cheaper, so it's practical to replace if more capabilities are needed.
I don't think the number of people in a room will give you meaningful information to tell you "how much to crank up the HVAC." Also, the HVAC systems in most homes aren't capable of even cranking up the HVAC in a particular room.
This is what the "Internet of Things" should be doing, but seldom does.