Yo is mobile messaging taken to its logical – if ridiculous – conclusion. Yet the app is strangely compelling, and is winning fans in design-savvy tech companies such as Foursquare, Path and Kickstarter, as well as plaudits on and from Robert Scoble, the tech blogger and professional early-adopter most recently famous for wearing Google Glass in the shower. As is fashionable these days, Yo began as a somewhat accidental side-project of another start-up. Yo’s co-founder and chief executive Or Arbel was asked by Moshe Hogeg, chief of image-sharing app Mobli, to make an app with one big button that could call his assistant without having to pick up the phone or compose a text message. Mr Arbel, a former iOS engineer at Mobli, was working on a stealth financial start-up, Stox, and said he didn’t have time. But sometime later, he remembered the single-character text conversations he had over WhatsApp with a friend: ? instead of “how are you doing?” and ! to reply “great”, or simply go back and forth saying “yo”. “We communicated without saying anything,” Mr Arbel said. Eight hours of coding later, he had combined the two into Yo, and shared it with his Stox colleagues. “They all loved the simplicity,” Mr Arbel says, “except one who said this is the stupidest app he’d ever seen.”

http://blogs.ft.com/tech-blog/2014/06/yo-the-new-app-that-takes-simple-to-the-extreme/