Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Digsby - Tagged makes it easy to meet and socialize with new people through games, shared interests, friend suggestions, browsing profiles, and much more.
Plivo - Plivo simplifies your customer engagement.
Facebook Messenger - Facebook Messenger is a faster way to message.