LocalChattr

LocalChattr is the Mac App Store's first solution for simple, unlimited communication over a local area network. Set up a chat room on your local network for everyone to access instantly and anywhere with the click of a button, even on Wi-Fi networks that normally charge for Internet access!

On a cruise ship with exorbitant wireless access fees, when all you need is a way to stay in touch with your family or friends? On a plane, and don't want to pay the insane Internet rates to stay in touch with others on different parts of the plane? Simply launch LocalChattr, click "Start Server", and you're set! You get access to a fully-featured chatroom hosted on the your own computer, meaning anyone on the same network can join and send messages without paying a dime, since you don't actually need Internet connectivity.