SMS delivery is the distribution of SMS messages to end-user mobile devices (i.e. Mobile Terminated SMS) or the delivery to an application of messages from mobile devices (i.e. Mobile Originated SMS). Delivery of SMS to or from an application can involve an SMS gateway operated by an SMS aggregator who would provide SMS APIs with which to communicate with the application.
See Melrose Labs Tyr SMS Gateway
Melrose Labs: Our mission is to deliver pivotal services in cloud communications across mobile, fixed-line and internet for enterprises of all sizes. These services allow organisations to improve their effectiveness, increase revenues and reduce costs when they use our cutting-edge communication services in business operations, and with customers and staff.