MeetingMogul - Join any conference call with one-touch
Twilio - Brings voice and messaging to your web and mobile applications.
CALLR - CALLR is an extremely helpful app for those who have to deal with call control protocols for their business. You can create a customized call control system that will perform a wide range of functions.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
MobileDay - MobileDay provides one-touch access into conference calls and online meetings from iOS or Android devices.
Clockwork SMS - Clockwork is an Easy Text Message API. An SMS API for Developers. Build powerful apps and include SMS. Signup is free, Try it now.