In followup from my iPhone programming presentation I have uploaded the presentation and sample Xcode project (Xcode 4.3.2) The sample converts between temperatures in celsius and fahrenheit. The sample shows how to setup the gestures in Xcode's interface builder, rather than in Objective-C code. Using the UIPanGestureRecognizer we can allow sliding input for the temperature conversion. The only code we need to implement is the action to take in response to a detected gesture.
Download the slides and sample code: