Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
Officevibe - Officevibe is an employee survey platform with the mission of improving company culture. Measure and improve your culture in less than 5 minutes per month, with our simple surveys.
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
TINYpulse Engage - Increase Your Employee Engagement. Instantly.
Kannel - Open Source WAP and SMS Gateway
15Five - 15Five software elevates the performance and engagement of employees by consistently asking questions and starting the right conversations.