Last weekend, I flew to and fro San Francisco and noticed something I'd never seen before. When you get off the plane and head for that room where your baggage takes a long, long time to tumble down a conveyor belt, you usually pass some limo drivers who are there to meet arriving passengers.They stand there holding up little signs on which they've chalked their passenger's name. But when I got to S.F., I saw five limo drivers and they were all holding up iPads, each of which had an arrivee's name displayed in a handsome font. And sure enough, there's even an app for that.