Was this site you were thinking of (linking to avc post since it's been shuttered for a while)? https://avc.com/2015/06/pegg/
That said, I never saw the site I had seen on mobile, so I don't know if it looked more like a mortar layout on a phone. And no one ever demoed that kind of chat functionality. So it might be a similar thing? Or it might just be an evolution of what I had seen. Either way, Pegg looks pretty cool. Sorry to see it didn't take off (either?).