Yes i found it: RN-XV WiFly Module - RP-SMA Connector - WRL-11047 - SparkFun Electronics but I'm a bit confused on how to use it. Correct me if I'm wrong, but i guess I've to connect it to the XBee shield. Is it the better solution?
Then I read that it's better to use also the USB host shield to be able to direclty program the Wifi shield, is it correct?
Thanks Ste