Octopush - Octopush is a company providing technology-based communication solutions, including SMS, Web solutions, and Email APIs.
Twilio - Brings voice and messaging to your web and mobile applications.
Clearstream - Clearstream is a SMS marketing and online texting software.
Plivo - Plivo simplifies your customer engagement.
Swift SMS Gateway - SMS Gateway is your bridge between the Internet and the world of cell phone SMS text messaging.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates