DNA scans would be no better
You leave DNA all over the place. Someone just needs to grab the straw you've been drinking out of, your lipstick, your hairbrush (yeah it sounds like women would be easier targets here...) or whatever along with your phone. Just like someone could get accurate scans of your face to produce that 3D model, or snag your fingerprints off a glass or your phone itself, and so forth.
Maybe if they embed a THz scanner it could map the blood vessels in your brain, though you might need to swallow something for contrast first...
Biting the hand that feeds IT
