This is a vague question, but if you simply want to know what key has been tapped you need to implement a delegate for input control that called the keyboard. For example if you are using a UITextView, then implement the UITextViewDelegate, wire up the control's delegate property to you class, and then implement the textView:shouldChangeTextInRange:replacementText:. When UITextView recognizes a change then it will call this method. You can then watch for the characters in the "replacementText" argument.
With UITextField use the UITextFieldDelegate and implement the textField:shouldChangeCharactersInRange:replacementString: method.
You can do other things with UITextField like change the Return button to a Done button in Interface Builder. The implement the textFieldShouldReturn: method. If it's called then run the resignFirstResponder on the object passed to the method.
Hope this helps.
