It works by sending a signal straight to the other persons phone without the need for any kind of data connection.
When you click send the app takes your message and repeatedly broadcasts it.
It also is constantly scanning for other people broadcasts through the same app.
As of right now it only sends text messages. No pictures or voice.
The app has a limited range due to the type of signal being used and my own testing shows 150 - 300 feet of range.
Also app messages are only temporarily saved. So use it for quick unimportant convo only!