The Sinch SDK for Android lets developers add voice calling and instant messaging capabilities to their iOS based mobile apps. The SDK handles signaling and audio management. In addition it offers support for:
App to app calling
App to phone calling
Instant messaging to single and multiple recipient
The Nexmo SMS API lets you send and receive text messages around the world without having to worry about which carriers the recipients are subscribed to. This tutorial shows you how to use the Nexmo C# Client Library to send and receive SMS messages from your ASP.NET MVC web app.
Twilio today announced that it has added support to its API for LINE, a popular free communication app that allows its more than 168 million users to make calls and send messages. LINE support is part of Twilio Channels, a feature of Twilio's API designed to build messaging experiences.