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.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Quickie - 3-60 second video calls with your friends
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Messenger Video Calls - Facebook Messenger, now with HD video calls
Plivo - Plivo simplifies your customer engagement.