What is the calculator app that hides text messages for iPhone?

Excuse me, could you please elaborate on the calculator app that is capable of concealing text messages specifically for iPhone users? I'm intrigued by the concept of an application that doubles as a calculator while secretly harboring the ability to store and protect private messages. Is this a legitimate and secure method for safeguarding sensitive information, or is it more of a novelty feature? Additionally, how does one go about accessing these hidden messages within the calculator interface? Lastly, are there any known risks or limitations associated with using such an app?