This extension is a very simple realization of progress bar component.
There are two classes:
Ext.ux.ProgressBar, which inherits from Ext.BoxComponent and
Ext.ux.ProgressBarItem, which inherits from Ext.Toolbar.Item and delegates to Ext.ux.ProgressBar.
The screenshoot and extension package are attached to the message. The api is simple but if anyone will have questions, I'll do my best to answer.