If you're a user of Apple's Messages application, or even third-party messaging applications like WhatsApp or Kik, then you could benefit from a new jailbreak tweak called ConvoProtect
by iOS developer Noah Saso.
ConvoProtect will give you some added security in these messaging applications by allowing you to lock them down on a per-conversation basis, and even hide the text from them. Doing this will prevent unwanted eyes from reading your text messages, and the flexibility that the tweak gives you is unmatched by free alternatives such as PrivateSMS7
For example, you can see above how we have password protected one of our conversations, and when we go to enter the conversation, we are presented with an alert