Twilio - Brings voice and messaging to your web and mobile applications.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Plivo - Plivo simplifies your customer engagement.
BulkSMS - SMS messaging service provider offering two-way SMS communication services.
SightCall - SightCall offers comprehensive real-time video APIs and Mobile SDKs that makes it simple to embed...
SMSAPI - SMSAPI.com is browser platform for bulk SMS and other SMS marketing solutions.