Standing in Pace MacGill, an art gallery in Manhattan, the art market researcher-cum-entrepreneur Magnus Resch opened an app on his iPhone and beamed. "Take a picture of an artwork," he said, handing over his phone, which displayed a salmon-red and white interface bearing the logo "Magnus".I did and then touched a button on the screen and the artwork in question - a 1973 image by the photographer Hiro, which was presented without a label on the gallery's wall - appeared on the phone, correctly identified. But the app didn't just display the artwork; it loaded, unprompted, the photograph's title, attribution, dimensions, price and a history of the work and exhibitions of the artist."It's the Shazam of the art world," Resch said.The premise of Magnus is simple and incredibly ambitious. The app aims to catalogue the existence and price of every artwork and to make that information publicly available. It's the Holy Grail of the art market. "I'm providing true access to the art market," Resch said. "People who've thus far been left out of the market can become buyers: they see comparable prices. We're equipping non-experts with the knowledge of an expert." ..