AS3 setChildIndex to front

Use yourContainer.numChildren - 1 to get the topmost index.

Before adding a button to the stage you can actually name it

  var myButton:MovieClip = new MovieClip();
  myButton.name = 'button1';

or

  var myButton:MovieClip = new MyButton(); //if you assigned a class name to your MovieClip
  myButton.name = 'button1';

With your example you could do something like this:

  var comp:Comp = new Comp();
  var monitor:Monitor = new Monitor();

  addItemButton( comp, "comp" , {x:100, y:200});
  addItemButton( monitor, "monitor" , {x:30 , y:50} );


  private function addItemButton(item:MovieClip , itemName:String , params:Object):void
  {
     item.addEventListener(MouseEvent.CLICK , clickHandler );
     item.name = itemName;

     // of course params is not necessary, just making a point of  
     // how to centralize your concerns
     item.x = params.x;
     items.y = params.y;

     addChild( item);
  } 

  private function clickHandler(event:MouseEvent):void
  {
     trace( "button clicked:" + event.currentTarget.name );
  }