This is a FREE application, which allows to silently reject incoming calls and send a SMS to caller.
If you are on important meeting, interview or presentations, you can just run this application and all your incoming calls will be dropped but callers will be send a SMS with text like "I am busy right now. I will call you back in 2 hours".
Application is as simple as it can be. There are just 2 buttons : activate/deactivate and change SMS's text.