Two ideas - I think recaptcha can figure out if people have certain mental health/neurological problems. Similarly, google voice and Siri could be used to detect people having a stroke or other health problems.

Obviously, tons of privacy issues, but I thought interesting blend of universal healthcare and machine learning.

Not sure if here is the right place or cogsci or computer science/programming or health or aviation/flying or...

An obvious, dead easy one for captchas is color blindness but I think more advanced systems could recognize dyslexia and more.

Voice based apps could be trained to recognize slurred speech (maybe hypoxia or stroke or diabetic crisis, etc) or other speech issues.