MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Twilio - Brings voice and messaging to your web and mobile applications.
Plivo - Plivo simplifies your customer engagement.
Restcomm - Next generation cloud communication platform that allows for the easy building of voice, video, and messaging applications.
Bandwidth - Bandwidth offers SIP trunking, Emergency communications, and Voice & Messaging APIs.
Melrose Labs SMSC Simulator - SMPP SMSC simulator to test SMS messaging applications.