Twilio - Brings voice and messaging to your web and mobile applications.
Melrose Labs SMSC Simulator - SMPP SMSC simulator to test SMS messaging applications.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
BulkSMS - SMS messaging service provider offering two-way SMS communication services.
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Plivo - Plivo simplifies your customer engagement.