What are some alternatives?
Dokku - Docker powered mini-Heroku in around 100 lines of Bash
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
Voxbone - Fully compliant, enterprise-ready voice and SMS on demand. Build local presence on a global scale with elastic SIP trunks and phone numbers. Try for free.
tsuru - Tsuru is an extensible and open source Platform as a Service software.
Twilio - Brings voice and messaging to your web and mobile applications.