The Sinch SDK for iOS 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
Twilio launched a beta trial for its new Notify API. The API represents a single, user-centric API that gives developers programmatic control over notifications to users in the format, and on the device most desired. Twilio hopes to send the right message, at the right time, to the right user.