If you're looking for a way of remotely-controlling an Arduino via your iPhone, but don't want to write the HTML for the interface... then this may be an option for you. The team from Red Frog Software have published an Instructable that details how to interface an electric garage door system with an Ethernet-enabled Arduino board. This setup can then be controlled over the Internet using their iPhone app. If you're in a hurry, it's simple and it works.
... or for more program space, I/O ports consider the Freetronics EtherMega - the Arduino Mega2560-compatible with onboard Ethernet, microSD socket and optional PoE: