I am writing an application for industrial use and the customer wants some gauge/dial similar to what they get on panel displays. A quick google search did not yield anything apart from ADA industrial control.
What other gauge/dial widget library (ideally in Python) exist for GTK?
Maybe you can adapt this "clock face" demo: http://www.pygtk.org/articles/cairo-pygtk-widgets/cairo-pygtk-widgets.htm
You may need to implement your own custom widget here. See http://zetcode.com/gui/gtk2/customwidget/ or http://www.pygtk.org/articles/writing-a-custom-widget-using-pygtk/writing-a-custom-widget-using-pygtk.htm