[barbegal]

That may be true when the screen is on, but from my experience scanning is not switched on in sleep modes on iPhones and most Android phones. I don't have definitive proof of this but I have never seen a modern phone be able to reliably scan whilst in sleep mode for any long period of time.

[dmitrygr]

it is on just at a lower duty cycle.

source: worked on this for a few years at googl, both chromeos and android