2 way communication wifi-iphone

helloo, I came across videos in youtube using ethernet shield to have a 2-way communication between iphone and the arduino ethernet using twitter. I used the wifi shield to do the same thing, but I'm stuck at the part where i receive a SMS notification. Because my location is not stated at the drop down page. is there an alternate method? and i want to communicate back to the arduino with a reply back to the received tweet.(e.g turning on the LED) How can i do that? Thanks in Advance! Any help would be greatly appreciated:)