Twilio - Brings voice and messaging to your web and mobile applications.
Plivo - Plivo simplifies your customer engagement.
smooch - Smooch connects your business software to all the world’s messaging channels for a more human customer experience.
VoxImplant - Voximplant is a software program that allows businesses to automate communications by setting up automatic communication systems in the cloud.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Google Cloud Speech API - Cloud Speech offers speech to text conversion powered by machine learning.