From the research I have done you can not fake micro expressions...

From the research I have done you can not fake micro expressions for pain. When they take the video the patient is still, so if they are trying to fake pain they are asked to be as still as possible and look at the camera. If there is real pain micro expressions are present which are picked up. If there is no pain you can't just turn on micro expressions, which is the bodies reaction to genuine pain. The only challenges I can see when this app moves into fraud is people actually inflicting injuries on themselves to turn on their micro expressions.