The ClickSend SDK in CSharp is available to use the HTTP API with the goal to integrate SMS messaging into websites and applications. With this service, users can send SMS, receive SMS, and track the status of messages. Useful to follow-up, notify clients, and create reminders.
Nexmo's mission is to take SMS global, putting messages on the 5 billion smartphones across continents and languages, with 800 carriers in 200 countries. As Alex Williams noted in Techcrunch, Nexmo raised $3 million from Intel Capital, NHN Investment Corporation and Initial Capital. Nexmo is:
"one of a new generation of companies that are disrupting the telco market. It streamlines the layers between the telcos and developers, removing the hubs by offering a carrier grade service based upon a worldwide network that gives companies like Airbnb an international messaging platform for communicating between buyers and sellers over SMS."
The RESTful and SMPP APIs save large multinationals from having to build their own infrastructure.