NextPlane - NextPlane offers cloud-based, scalable unified communications federation service for the enterprise.
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Voxer - Turn your phone into a Walkie Talkie. Don't waste time on phone calls and voicemails.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Sameroom - Chat interoperability-as-a-service
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.