Jeremie Miller almost brought on a golden age of instant messaging. He invented XMPP — often referred to as Jabber — the common language used by many IM apps to talk to to each other. If your friends used AOL Instant Messenger or ICQ or even Yahoo! Messenger, it was possible for a brief period in the mid 2000s to use any app you wanted to talk to friends. Some chat apps let you group all your chats into tabs instead of windows, while others let you add wallpapers to your chats or even skin the entire app’s user interface. Then, as IM on computers gave way to smartphones, it all fell apart.

One big problem was that Jabber wasn’t designed to keep up with devices popping in and out of connectivity. In 2009, WhatsApp began its global conquest on the iPhone using a custom version of Jabber that no other apps could talk to, and now it boasts over 350 million active users. Skype and later iMessage took hold, cementing the new “walled garden” approach for IM apps. Google, once a champion of XMPP, dropped support for it in its latest Hangouts chat app. Now, dozens of closed, insular messaging networks compete for your attention.

Jeremie Miller was not happy. “I don’t call it a communication system if it’s closed. It’s just some black box you drop a message into and somebody might get it on the other side,” he says. After selling his startup Singly, he was ready to get back into the chat game, but this time, with mobile devices at the forefront.