Seems like if you had an SLR or view camera with a fast lens, you could set it up next to the 'real' camera and peep it to make sure the subject hasn't moved.

I don't quite understand the attraction of the razor-thin DOF done on purpose. I understand the appeal of isolating your subject, but to me, the subject is the person, and to me it seems basic taste that the person or at least their face should be in focus.