This app was removed from the App Store.
iOS iPhone Social Networking
Send and receive multichannel messages to nearby people acoustically! No network connection needed! Embed the audio in your music to send "secret" messages.
Banshee makes up to five channels of messages, up to 60 characters long. You can record these sounds, which sound like crickets, and have your friends decode the messages.
It's a little like the days of acoustic modems.
more at: http://jhhl.net/iPhone/Banshee.
Much better decoding, dashes for "unknown" characters.