But when we move to wearables, session length will drop from two minutes to two seconds, Libin said. The challenge will be figuring out how to make someone productive for one second at a time, 1,000 times a day. Apps are irrelevant in the world of wearables, because “when any given interaction is a second long, you definitely don’t have time to think about apps,” Libin said. “It has to be more of a service.”