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.
A very simple chat client that works over bluetooth (so no internet connection needed!) to find anyone running the same program near you, and chat with them. Perfect for places where you need to chat with someone nearby but can't (like a classroom--ahem!). Start the program on both phones or iPod Touches, pick your friend from the list, and chat away. When the program quits, the conversation disappears, so no record of it--no problem! Pinch to change font size so you can read your conversation (or hide it) better!