To be able to display values in the game GUI and be able to change them is not very hard, here's an example (not tested)

public float myVariable = 5;
public bool myOtherVariable = false;

public void OnGUI () {
   myVariable = GUILayout.HorizontalSlider (myVariable,0,100);
   myOtherVariable = GUILayout.Toggle (myOtherVariable);
}

This will display the values on screen. There is no good way to display numbers-only fields in the game gui though, so I used a slider in the example instead.

To display stuff in the editor is a bit more tricky (or at least not as common or well documented) But you can read on here to get started. Extending The Editor - Unity Reference Manual

Hope it will help you get started.

this is another example on how to display a variable.

Using UnityEngine

Using System.Collections

public class exampleScript : MonoBehavior

{

public float myVariable = 5; 

public void OnGUI () 
{ 
    GUILayout.Label((int)myVariable) 

} 

}

what (int) does is typecasts myVariable to an integer, in other words it just drops the decimal point and doesn't round. I find type casting comes in handy when you need a float and integers wont work or visa versa.