Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
TextMe - TextMe is a free calls and messaging application at both local and international levels.
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Talkatone - Android App on. Google Play. Stop paying for cell minutes, texts & landlines; Turn your iPad or iPod touch into a phone; Call/Text even in areas with bad cell coverage; Call/Text when travelling without paying for expensive international minutes.
Plivo - Plivo simplifies your customer engagement.