Ubisoft have released an app that takes on the themes for Watch Dogs called H_ide, which allows you to encrypt things like messages, pictures and your voice.
I’ve had a bit of a play around with it and it seems like something you could have a bit of fun with. There’s some voice change options when sending voice messages, and the encrypt message bit changes your words into a mixture of letters and symbols. The picture encryption seems to just change it to a blue, distorted screen.
You can also decrypt messages sent by others using the app, so it seems the real depth will come from using the app with others. Of course, use it responsibly, and don’t use it to mess with people unless you’re really good friends.
H_ide is free on both iOS and Android.