The ScaleSlider is a replacement for the ZoomPanel, using an Ext.Slider. It is also possible to add a special tooltip plugin, ScaleSliderTip, which will show the zoom level, scale and resolution while dragging the slider (the content is configurable of course). The slider can either live outside the map for usage in other Ext components, or we can use the addToMap() method to add it to the map as if it were a map control.
Below we have the slider on the map with a custom tip:
Here we have another slider, connected to the same map, but living outside and with the default tip: