What are some alternatives?
Slack - A messaging app for teams who see through the Earth!
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Facebook Messenger - Facebook Messenger is a faster way to message.
Tox - Send messages, files, create groups and make Tox to Tox audio and video calls. Securely.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.