The Arduino WiFi Shield is a new tool from Arduino guys.
They decided to create a shield with many features, and it costs more than the other shields (more than twice than the Ethernet shield).
The reason why they made this shield so complex is to have the possibility to use it alone, without an Arduino attached to it. The “high” price could then be justified by the fact that you won’t have to spend the money for the Arduino but just for the shield, and it will also consume less power.
One useful hack to improve its usefulness as a stand-alone gadget could be to configure the SPI of the AVR32 to act as a master and connect the Slave Select of the SD card to an IO of the AVR32, so that the micro-controller can directly access the storage.
Anyway, this shield enables the possibility to really have an autonomous device (even with an Arduino attached), without wires for communications or power. With the already existing ZigBee modules you needed another ZigBee tranceiver to communicate with the Arduino, and those are not so common. Even with Bluetooth you need something like a laptop or smartphone around to connect to it. But the WiFi shield lets the Arduino communicate with the router that many people already have at home, and connect to free access points around the city; the connection to the network is more direct. The possibilities are vast, as far as to revolutionize the “Internet of things“; who knows what the makers around the world will invent.