Ben Lovejoy, 9to5Mac:

The granted patent could use the Mac’s camera to do two things. First, it would avoid timing-out into sleep mode when there’s someone in front of the machine.

and, after posting a big chunk of “patenteze” from the granted patent:

My reading of that and the accompanying illustrations is that the Mac can automatically wake and log you in, even if it is in sleep mode when you approach it.

Sounds good to me. And, I’d add, it sounds like that “second sensor” mentioned in the patent is your Apple Watch, though could be the iPhone in your pocket, too.