This app will allow you to encode and decode messages. It works independently of any messaging service so you will have to write your message into the app and then copy the output to the service of your choice. This allows you to have an extra layer of security in your communications. In the event that someone has the pin to your phone then this app will make sure that even your clear text messages will be unreadable. You will need to have an agreed upon password to use with friends so that they can decode your messages.
Please note that this app is not meant as a major security enhancement to your phone and any significant government agency will be able to crack this system without too much trouble. It is recommended that you use other messaging services that have their own security if you are concerned about three letter agencies delving into your personal information.
Credit for icons goes to cooltext.com text generators.