A lot of computers and most Macs have cameras pointed at the user.
Why not make facial recognition an option for log in instead of a password or; an option in addition to a password too?
iMacs seem to be all over the place in use by doctors, lawyers, professors, researchers, designers, and other professionals in particular who might like that instead of a password or in addition to it. Doctors in particular are so busy and have so much to remember. Most of which is a hell of a lot more critical than a password to access confidential data or records.
For iPad, if more computing power is needed, tie it into the doctor's office iMac via the network to chomp the facial recognition points.
Doctor, walking about, needs to access patient data on iPad. Knox request facial recognition to open file on iPad. Lives saved!
School teacher does not want students to access data on iPad while back is turned, etc.