I saw this article earlier today. A ControlThink Z-Wave SDK wrote an application which monitors the status of bathroom stalls (available, occupied, or "warning: recently occupied") and then uses a Silverlight-powered Windows Vista SideBar Gadget to display the info.
Very nice.
http://blogs.msdn.com/coding4fun/archive/2008/08/13/8859880.aspx
Chris
ControlThink