It used to be that back in the day, platform-exclusive messaging apps were a thing. For example, BlackBerry Messenger used to be so popular that people would actually buy BlackBerry phones just to use it. These days, the focus is more on cross-platform compatibility.
However, there are still some holdouts, such as Apple’s iMessage which is still exclusive to Apple’s iOS and macOS devices. However, thanks to the work of Eric Migicovsky, the CEO and founder of the Pebble smartwatch, he has since created a new app called Beeper that will bring iMessage to multiple platforms.