messageVIP (http://www.handango.com/ampp/store/PlatformProductDetail.jsp?siteId=308&platformId=4&productType=2&productId=140892&sectionId=0&catalog=1&topSectionId=-1) is a program which allows you to hide the meaning of SMS. You set it up so that letters are substituted for others, thus giving a basic form of encryption. The program works with both outgoing and incoming messages.