Linkello - Video calls simplified, no installation required.
Video SDK from Zoom - Build fully customizable video-based apps
jTorchat - jTorchat stands for Java Torchat, and is a complete rewrite of the popular p2p IM messenger Torchat
Amazon Chime - Online meetings and video conferencing
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
AuthKey.io - SMS API and WhatsApp Business API