The Sinch SDK allows developers to add voice calling and/or instant messaging to mobile apps. It handles features like signaling and audio management while and also allows for the creation of a user interface.
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.
Gecko Landmarks is working on an easier way of giving directions. The theory behind their madness is that “everyone thinks in landmarks”. They took this idea and ran with it. In fact they have run all over the world with this idea. They have now collected landmark data for every country in the world. Most of this data is now available in the Gecko Landmarks API.