Viber - Free and secure calls and messages to anyone, anywhere. Keep your conversations going no matter where you are.

Twilio - Brings voice and messaging to your web and mobile applications.

MiVoice Business - MiVoice Business is a business communication platform that delivers voice, messaging, mobility, presence, conferencing, collaboration and applications.

Bandwidth - Bandwidth offers SIP trunking, Emergency communications, and Voice & Messaging APIs.

Screenleap - Screenleap is a web app that lets users share their device's screen over the Internet. These screens can be a desktop computer monitor or a smartphone screen or anything else that can load a web browser. Read more about Screenleap.

Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates