I've just applied for visas for an upcoming holiday. I thought they did it pretty well - you upload a photo of your passport (info page) and a photo of yourself taken that day. It scans the two and gives a % similarity, and if it's over some level, it lets you continue.
I scored 78% with different beard and hair colour (my passport is from 9 years ago - hair is a lot whiter now!)
Obviously the problem there is that not everyone has a passport. But if you have a driver's licence which most people do, it can compare the details from that to the state's records to ensure the licence is valid, then compare the photo to one taken today, compare your address to the electoral rolls then take you to a secure area to cast your vote.