Twilio - Brings voice and messaging to your web and mobile applications.
Video SDK from Zoom - Build fully customizable video-based apps
OpenTok - Build a custom video experience using our robust APIs, or add plug-and-play video to your website in minutes using Video Chat Embeds. Start Building for FreeTalk to SalesTalk to Sales .
Amazon Chime - Online meetings and video conferencing
Plivo - Plivo simplifies your customer engagement.
AuthKey.io - SMS API and WhatsApp Business API