Mininigma
Mininigma is a complete Enigma Machine simulator for your Apple iOS.
Basically, Enigma was a cipher machine used by the Germans during World War II for the encryption and decryption of secret messages. It looked like an old typewriter with some extra features.
You can use Mininigma to encrypt messages, send encrypted messages by email or decrypt messages sent to you. Being fully compatible with the real Enigma means you can also use Mininigma to decode any of the original messages which can be found on Internet.
Mininigma supports Copy/Paste to allow you to interact with any other application on your device. You can even copy/paste machine configurations in an encryptable string to send them along :)
Mininigma can accurately simulate different types of machines: The Enigma I, M3 and M4, Railway, G-312, or Swiss-K, with some others coming in the future. You can read more about these in the Wikipedia.
You can actually select between the different machine types and setup them as you would with a real one: choose rotors, configure them, or use a plugboard to switch letters. All at the tip of your finger.