Crypto is an awesome app that will let you communicate with your friends secretly over social networks such as Twitter or Facebook and also via emails.

Functions: Type anything into the textbox on the top and select an output conversion scheme and tap encrypt to change text into:
Binary
Hex
L337 (LEET change numbers to letters and letters to numbers e.g. E/e = 3)
Custom (Make your own scheme)

The custom function lets you create your own scheme quickly and easily. Set up the same scheme on your friend's device to chat secretly online!
Creating a custom scheme is as easy as tapping on the left side of the screen then tapping the right side of the screen on the desired characters!
View the swaps in your custom scheme simply by viewing the "View Custom Scheme" button.