xwatch

logfile monitor that displays in an X window.

The displayed logs are colour-coded according to severity. Basically, you get to see what's going on _during_ say a break-in, instead of having to check the logfiles after the damage is done. Of course, you need to have the syslog daemons configured right, so that the logfiles are created. Xwatch reads options from its commandline as well as from a app-defaults resource file.