[adrianN]

Reporting an approximate number of people is not a trivial task, even with a real camera. Depending on what exactly you mean with "approximate", of course.

[Animats]

0, 1, a few, many. Just enough to tell you how much to crank up the HVAC.

[kinsomo]

> 0, 1, a few, many. Just enough to tell you how much to crank up the HVAC.

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.

[Animats]

True. The market for this is schools, offices, and hotels, where the people load changes drastically and the HVAC has to react to that.

This is what the "Internet of Things" should be doing, but seldom does.