This example shows a simple popup showing the position that was hovered.

To achieve this effect, the GeoExt.component.Map is instantiated with pointerRest: true, so that the events pointerrest and pointerout become available. Whenever pointerrest is fired, an instance of GeoExt.panel.Popup is positioned and its HTML updated.

Have a look at gx-popup.js to see how this is done.