Evernote is easily one of the "it" apps of recent years. But Phil Libin, the founder of the popular cross-platform note-taking system, says apps, in general, are not the be-all-end-all of mobile computing. He went one step further, and predicted they are not long for this world.

Yes, he actually said it: "Apps will be obsolete."

Currently most Evernote users interact with it primarily on their mobile phones. But when Libin looks to the future of computing, he's extremely bullish on wearables. He said Thursday at the exclusive f.ounders conference in New York City that while productivity on desktop computers flows in cycles of two-to-three hours, productivity on a cell phone screen is achieved in much smaller chunks of time.

"It's not just that the screens got smaller, but on phones, you have to solve the problem of 'how do you make someone productive for two-to-three minutes,'" Libin said. And apps are ideal for short, minutes-long interactions.

Libin is a big believer that within a couple of years, smartwatches and eyeglasses will be mainstream. In other words, computers will be worn rather than held in a palm. And that will inherently change how individuals interact with the programs or systems the computers run--including Evernote.

"When you go to wearables, the session length is going to drop to a second," Libin said. When a computer user is only going to spend a second or two at a time to glance at a watchface or hologram, an app--as we think of them now--wouldn't even have time to open.

So, Libin said, the problem Evernote, which has 90 million users--along with other app and media companies--is: "how do we make someone productive for a second at a time?"

I asked him what we'd call an app that isn't packaged as an app--an app that's just there.

"I don't think we have a word yet. Let's just call it a service," he said. "But I'm horrible at naming things, so who knows."