The Apple Blog’s Geoffrey Goetz shows how to use an iPhone or iPod Touch to control a Keynote presentation on an iPad. This would be especially useful when connecting the iPad to a large display using the dock connector.
One of the best new features in Apple’s updated iWork suite for iPhone and iPad is the ability to control a Keynote presentation on your iPad (probably ideally connected to a larger screen) using your iPhone. Please note that the following requires both devices to be on the same local Wi-Fi network, rather than working with a device-to-device Bluetooth connection, and that you must also have the Keynote Remote ($0.99) and two iOS devices.