[Wlug] workspace selection by app?

Is there a way to have an application start in all gnome workspaces? For my particular need, I am using xmessage to inform me of specific events on my machine. To make it harder to lose track of the xmessage (pop-up) window, I'd like it to display in all my workspaces. I figure there's some magic setting in gconf (or, even better, an X display setting), but I can't find any documentation on it. Any ideas? Thanks, Bill