Last month, Guru Labs taught a custom on-site class at BYU. Happily, this gave me a chance to visit former co-workers. Doing so was not only enjoyable, but also educational. While I was there, Jack Harris shared a trick with me. He'd discovered that that the Distort screensaver could be configured to display regularily updated information while keeping the monitoring system protected.
The Distort screensaver takes a picture of your current desktop then displays it slightly modified, or "distorted". Just start one of more monitorig tasks, then start the locked screensaver, and you've got a password protected, regularily updated monitoring station. The following is my opinion of how best to configure it.
Screenshots were taken using xscreensaver-demo to configure the X screensaver. On Fedora Core 3, it can be found under Applications > Preferences > Screensaver. On Ubuntu, it can be found under System > Preferences > Screensaver. Unfortunately, I couldn't find an easy way to get this same effect in KDE on SUSE.
Start by making sure that Distort is the only screensaver used. Cycling after one minute will cause Distort to refresh its picture of the desktop, thereby displaying any updates from the monitoring tasks. Locking the screen after zero minutes will make sure that the system is password protected as soon as the screensaver starts. Note, however, that this does not prevent any anyone from switching to another virtual terminal by pressing Alt+Ctrl+Fn.
Under the "Advanced" tab, make sure that the screensaver has permission to take a picture of the desktop. I recommend a one second "fade to black when blanking" to avoid an annoying flash each time Distort switches to a new picture of the desktop.
Clicking on the "Settings" button of the "Display Modes" tab opens a window that allows configuration of the Distort screensaver. Change the setting to whatever you prefer. I personally found a single small, fast moving magnification to be the least distracting.