Hey... I don't have 10.4, nor am I aware of how easy or difficult it would be to create a Dashboard app, but I have an idea, and if one or more people want to help, that would be awesome.
Dashboard is the browser. A widget (not an app, really) contains XHTML pages and JavaScript code, mainly, AFAIK. Haven't really looked into it, but you can download some widgets at thedashboarder.com and take a look inside the packages.
Im thinking of something that would give our techs direct access to new and recent tickets without having to log into our question system. So, basically, just a widget that holds a username/password and would just parse data from a given url formatted in a way that is best for the widget to parse.
The info on that page pretty much explains the basic fundamentals of it all..
You could theoretically start developing based on what info is in there...
I'd love to help out with making widgets, but i dont really know much nearly anything about javascript and xhtml. But if anyone needs like some sort of graphic for their widget feel free to ask me, i can do some pretty mad aqua stuff.
Maybe macosx.com should form a widget making group ???