is this possible? it mould be way more reliable to use the detected unlock codes on the door to know who is at home, this shouldn’t be hard with a virtual presence 
is there a way to change presence from code? this would be a great smartapp
Looks like there is a “Simulated Presence Sensor” in the list of things. I’d have to experiment with it a bit and is how to turn it “on” or “off,” or if that’s even possible.
Assuming it’s possible to change the status of the simulated sensor, then an app to change it because on code entered doesn’t sound like it would be too hard.
However, the bigger question, in my opinion, is how would you indicate to ST that you’ve left? Without an easy way to do that you end up losing a good chunk of the benefit of the sensor.
I think this is as close as you can get w/o presence sensors.
Possible? Sure. That would detect if someone was present. How would you know when they left?
…Maybe a button to press when you leave?