This is very powerful tool to add to arduino, why?!! Because this shield add USB Host capability to Arduino and you have ADK (Android Development Kit). Simply, you will be able to plug USB mouse, USB key board or any other USB device into Arduino.
It also allows to use your Arduino to interface with and control any USB slave device such as digital cameras, bluetooth dongles,etc.!. Using USB host shield enables the use of cell phones in Arduino projects to exchange data via SMS.
This new version of USB host shield is compatible with both Arduino uno and mega just out of the box.The following device classes are currently supported by the shield:
HID devices, such as keyboards, mice, joysticks, etc.
game controllers - Sony PS3, Nintendo Wii, Xbox360
USB to serial converters - FTDI, PL-2303, ACM, as well as certain cell phones and GPS receivers
ADK-capable Android phones and tables
Digital cameras - Canon EOS, Powershot, Nikon DSLRs and P&S, as well as generic PTP
Mass storage devices, such as USB sticks, memory card readers, external hard drives