CatchUp is Facebook's NPE team released a new app that puts emphasis on facilitating group phone calls. It's essentially Messenger Rooms, but for voice calls and lets users see when friends are online, and who's up for a call. It's also available to both iOS and Android users in the US.
Per its app description:
"Catching up has never been this easy. See who's available and effortlessly join one-on-one and group calls. Never play phone tag or make an appointment to call someone again. Keep in touch more, think about it less. Any time you're free to talk, CatchUp!"
The app pretty much works like Messenger - you can make calls within Messenger already. CatchUp on the other hand, lets users see who's specifically available for a call, and could prove beneficial in regions with limited connectivity and people prefer phone calls.