"detect the lack of any electromagnetic field paired with no vibrations at all and colder temperature"
You go hiking far outside of civilization and go to sleep in a tent, there are no electromagnetic fields around you at all(that the phone can detect anyway), there are no vibrations at all, and the temperature is cold because the phone is not on your body.
Or for a slightly more realistic example - I stayed with a friend recently who lives in a house from the 12th century - walls in there are about a meter thick, in certain rooms there is absolutely zero reception from any network, wifi doesn't penetrate at all. The no vibrations and low temperature points also apply there.
He's suggesting some sensor checks, not giving a total framework to account for every edge case. If you were to implement something like this, you would take many cases, including edge cases, into account.
