Use ArduActivate to trigger your Arduino with you iPhones GPS. This app works with the unmodified demo of tinywebserver of Arduino with Ethernet shield. It triggers the digital out when you are in a circle range from your home or wherever you want. You define a circle center (base) and a radius, and when you are close enough to the base, the iPhone sends to Arduino the activate command. Useful for example for opening gates when youre coming home and dont what to use your remote... as when youre in your motorbike... For more info, pictures and video visit: http://www.totemc.com/home/arduactivate
Istruzioni in italiano qui: http://www.totemc.com/home/arduactivate/arduactivate-ita-en
"Continued use of GPS running in the background can dramatically decrease battery life."