I still think most dogs will be able to recognise a face in the screen (especially when combined with your voice), but a larger size would be better. (thedogclinic.com)
It can recognise your face even if you wear a big hat, and will discount someone wearing makeup to resemble your face. (t3.com)
At last i got this face unlock update, but we can unlock it by double tapping the screen, no need to press the power button, it instantly recognises the face. (gogi.in)