room occupancy sensing

[ano]

Guessing those will run a bit more than $20 each, though

I'm not sure how much the sensors cost, but you can probably purchase the entire company for about $20. Their stock trades at $o.ooo5 a share so I wouldn't put in a big order for sensors today.

 

[adamf663]

A problem I see with IR/ultrasound/microwave sensors is the presence of pets.  How do you detect humans, but not cats'n'dogs?
 
I'm  leaning to using some kind of id carried by household or detection of smartphones.  That wouldn't work too terribly well if the smart id/phone is left in a room or if it is impossible to get everybody to participate.
 
I wonder if facial recognition technology could be used to recognize what the pets look like and ignore them?