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
Kannel - Open Source WAP and SMS Gateway
ReviewTrackers - Software that generates new customer reviews, engages your customers and lets you listen and...
Bulk SMS Services - Sending Bulk SMS to the customers will engage the customers with your business and new offers.
Reputation.com - Reputation.com is a solution for tracking and improving online reviews, social media, and local search visibility for businesses.