Wikipedia
Shoutr
shoutr is a mobile application that allows users to transfer data of any kind between Android-powered devices. What is unique about shoutr is that it works without an internet connection or pre-existing network infrastructure. All that is needed are two or more Android devices equipped with Wi-Fi technology. All data sent with shoutr is protected by WPA2 encryption.
The technology behind shoutr is based on the WiFi capability built into the respective Android device. This is used to connect devices directly: One device opens up a WiFi hotspot; other devices connect to it and get the data - this does not need a WiFi hotspot around.
According to Google Play, shoutr is available for Android devices from Android 2.2 (Froyo) on.