Montreal resident Martin Reisch was travelling to the U.S. to drop off some Christmas presents when he realised he forgot his passport. Being two hours from home already, he wasn't about to turn back.
As he approached U.S. customs, he thought he'd attempt to use a digital copy of his passport that he had on his iPad to get through customs. The border official was a bit annoyed, but let him through. A Canadian official also let him through on his way back home.
Reisch wasn't travelling by plane, but was making a land crossing which could be the difference between using the iPad copy at an airport and not being allowed to travel. This may not work again, or for anyone else, but it goes to show a digital copy of your identification can definitely help, at the worst of times.