Full code after the jump.

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/04/06/using-the-tooltipmanager-class-to-determine-the-current-tool-tip-in-a-flex-application/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            import mx.controls.ToolTip;
            import mx.events.ToolTipEvent;
            import mx.managers.ToolTipManager;

            private function button_toolTipShown(evt:ToolTipEvent):void {
                var toolTip:ToolTip = ToolTipManager.currentToolTip as ToolTip;
                Alert.show(evt.toString(), toolTip.text);
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="button"
                label="Roll over button to display tool tip"
                toolTip="The quick brown fox jumped over the lazy dog"
                toolTipShown="button_toolTipShown(event);" />
    </mx:ApplicationControlBar>

</mx:Application>