basically a smartphone size polygraph or a software version of Dr. Lightman ("Lie to me"). Heart rate, eyes expansion/contraction, pattern recognition on face muscle twitching, like of lips, eyelids, ... Could something like it speed up, for example, TSA lines at airports? Automated "checkout" lines like in grocery stores - face camera, hand palm on touch pad, "Are you a terrorist with a bomb? Choose Yes or No" (reminds a gun vending machine scene from South Park if i remember correctly :)