The Sinch SDK allows developers to add voice calling and/or instant messaging to their web apps. It handles signaling and audio management and also provides the ability to create user interfaces. This first release supports only instant messaging and app-to-phone calling with app-to-app calling to be added at a later date.
Our API directory now includes 239 messaging APIs. The newest is the Parseco API. The most popular, in terms of mashups, is the Twilio SMS API. We list 169 Twilio SMS mashups. Below you'll find some more stats from the directory, including the entire list of messaging APIs.