avaamo - Simple, Secure Business Messaging
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
SupportKit - Embed Zendesk support into your iOS app with 1 line of code
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Fleep for Business - Simple, open collaboration and chat with admin capabilities
Expensive Chat - Chatroom where you pay per letter