This is news some time ago but I've just seen the video of how Jorge Colombo used an app called Brushes on the iPhone to create last month's New Yorker cover.
It just shows how much mobile creativity and computing has come in the last couple of years. There's a short video of how Jorge created the cover at Onxo Gadgets.
What's amazing is that we're only scratching the surface of what the creative mobile society can do with their mobile devices. I'm more than certain that we'll see more amazing things in the coming years.