Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
Birdeye - #1 most trusted reputation and customer experience platform for local business
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
Reputation.com - Reputation.com is a solution for tracking and improving online reviews, social media, and local search visibility for businesses.
Kannel - Open Source WAP and SMS Gateway
Podium - Podium helps your business get more customer reviews, manage customer feedback, customer interaction, and online review management from one software.