Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
PackageX Receive - PackageX Receive digitizes package-receiving operations and delivers world-class package management solutions.
Kannel - Open Source WAP and SMS Gateway
AfterShip - AfterShip is the shipment tracking API for ecommerce businesses and marketplaces.
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
DelivApp - Software for managing online ordering, delivery and loyalty for multi-unit restaurants