If you get a little concerned about the security of messages sent from your handset, then you might want to take a look at Sicher. It is one of those apps that encrypts messages so you can be sure your communications can't be spied on. Not only will it encrypt the text of a message, it also secures pictures, voice messages and documents.
As well as one-to-one chat Sicher can accommodate groups. The encryption means that only you and the recipient can read messages and open attachments. Also, you can set up a self-destruct timer so that messages are deleted from your handset and that of the recipient, for good, at a set time. Chat history for participants in any exchange can be deleted too. Messages aren't stored on servers, either, so once they are gone they are well and truly gone.
OS: Android, iOS, Windows Phone