Arduino and iPhone via WiFi

Hello,

First of all, I can control Arduino from iPhone by using Processing and TouchOSC app.

But my task is to achieve a control wirelessly "without using a PC" in between. I need to control Arduino directly by iPhone via "wifi". I should only use an Arduino, a shield, an iPhone and the wifi network. This is the task i am given.

I am really confused which way to use and which shield to buy.

I would be so glad to have your opinions.

Regards,

Zoomkat knows the answer! There are threads on here explaining the code. How about the WiFly hardware?