Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
API to bot - Convert your API to Alexa skill or Google Home app in 5 mins
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Jovo - 🗣 Build cross-platform apps for Alexa and Google Home
Plivo - Plivo simplifies your customer engagement.
Voice Principles - Guiding principles for voice design, all in one place