There are some tools that will allow you to embed a screensaver in the desktop (there are hundreds: it must be a sample app in some MacOSX programming book; look on VersionTracker) and there are screensavers that have uptime-type information in them (ShowOff, among others). I think I'd go that route.

There are also tools that will embed Safari in your desktop. You could point it to a local file that reloads, maybe. I like the first option better.