In a perfect world this would work - I would have 5 nest boxes for my 5 chickens, each nestbox would have an optical eye scanner and would only allow the chicken assigned to that nestbox into the nestbox. A small door would close behind the chicken - this would eliminate the other hens seeing their friend in the nestbox and standing in the center of the coop shouting "Someone's laying an egg! Someone's using MY nestbox!". When the hen was done laying her egg or if she changed her mind (as they do 50 - 100 times before laying an egg) there would be a small button on the inside of the nestbox that she could press and this would open the door of the nestbox. Ta Da!!!
You could RFID chip your hens and have the auto-opener respond to specific chips.. Though really, that's a bit scary to think of someone doing -Spooky
Do chickens have unique footprints? hmmm I am not too sure about that one. Maybe with injuries or etc etc. But if we did any of these it would eliminate the joy we have on cold mornings having to lift 4 girls out of one nest box to find NO EGG YET! Only to repeat this procedure a couple more times before there are suddenly 4 eggs in there.