RapidPro - SMS Channel

The RapidPro SMS Channel app allows you to use your phone to relay messages when building interactive SMS applications. Take advantage of our powerful Flow engine. With Flows, anybody can set up or modify a complex SMS application without the need of a programmer or expensive consulting company.
Using a basic Android phone, you can launch your application instantly in any country while avoiding expensive set-up costs or external technical support.

See http://rapidpro.io for more details.