The author writes:
The brain of the system is really on the arduino or the web page the phone requests. . . The phone just passes any data it sees back and forth. . .For the phone app to run, it needs the URL of a server and the path to a web page. Once that information has been made available by the arduino board, the phone will request that web page anytime it sees a # on its serial port. . . Additionally, any results from the web page requested are sent back to the arduino via the serial port. So, if you just need to request data from the web at a set time frame, the arduino sketch needs only to send a # from time to time and wait for the result. If you need to pass variables to a website, the arduino must pass a string with those variables and end the string with a #.
Arduino mobile processing: [Link]