The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Teddy Newell:
Live a double life as a spy with iCipher! Send coded messages to your friends! Decrypt encoded secrets sent to you! Hide top secret information from prying eyes! iCipher lets you encrypt secret messages with 5 different secret codes. Easily send your coded messages by email, or copy and paste your message anywhere on your iPhone. Plus, type or paste enciphered messages into iCipher to decode them. You can be just like a spy with the quick encryption of iCipher. Features: Encode and decode text with 5 different coding terminals: Letter Substitution Invisible Ink Box Cipher Morse Code Number Substitution Someone looking over your shoulder? Quickly erase your message and settings with the touch of a button. Simulates flash paper secret text disappears in a flash of virtual flame! Email encoded messages from within iCipher Customizable coding settings Supports Cut, Copy, and Paste to import and export messages Intuitive Interface Convenient Help information Tips & Tricks for each coding method Saves settings and most recent message Security: Lock access to iCipher with a custom PIN