[TedDoesntTalk]

I thought it also used the bluetooth aspect of the app to know if you're home? IOW, if the app can ping Nest over bluetooth, the Nest knows you're home.

[withinboredom]

How does it know who’s phone belongs to the people who live there?

[TedDoesntTalk]

I think you have to pair the app. Otherwise anyone could control your thermostat, even from outside your front door.

[withinboredom]

But what if you leave your kids at home? How would it know their phones? I wouldn’t give my kid the power of the thermostat, the pranks would be endless…

[TedDoesntTalk]

It also has a motion sensor, as OP mentions.