4.6 Custom Inspector using "object function call" as in InputField Inspector

I want to use the Inspector tool that is used to select a gameObject.(function) in a similar manner that the new 4.6 InputField uses for activating function when handling events (On Value Change, End Edit) in the inspector (I can select a gameobject, function, and even pass a value). Is this possible with a custom inspector? Can someone point me in the right direction? I don't see which method to use for the EditorGUILayout class when building a custom inspector class.