A simple encryption system for the masses!
Just like spies of old, write a key and a messages. Press the lock and you have an encrypted text file to send to you friends, lovers, secret lodge mates, evil organization boss or just to keep safe for yourself. Like a dairy that your big brother would never read!
You can name you file "Sales.xls", "Presentation.ppt" or any other name that wouldn't raise any eyebrows.
Of course, if you want someone to read the message, you tell them the key (in person is better. Check you are not being followed!) and send them the file. Using the same app on their phone, they can input the key and read the message.
The best thing since the "Decoder Ring"!!