Phone App for Attendance

I just got back from our Tuesday Church service. I really enjoy this service and have been able to learn a lot. After the service got over we were just having a little chat and a friend of mine was talking about how cumbersome it gets to note the attendance. she was casually asking if there wud be a better way for doing this than a pen and paper ? Got me thinking and i got this idea.. Think of a phone app that would scan the images of people who come in (through a built-in video camera) and using facial recognition just matches them to their names and marks their attendance. If someone is new, it would just show their image with no tag / name and once we assign the name, its all set for next week. The rough part would be that we have to make sure that the phone scans everyone who comes in.