syslog-notify, a utilty for modern Linux (and other Unix-like) desktops, provides a pop-up display for messages that would otherwise be written unnoticed to the system logs. The choice of messages to display (from all messages to only the most critical) is completely configurable through the standard syslog configuration files. Popups are handled via the freedesktop.org notification standard, and thus are fully integrated with the desktop environment.
Fido is a multi-threaded file watcher which searches files in real time for user-defined patterns. When it locates a match, it runs a user-defined program. It is useful for monitoring log files for issues and responding to them. It was designed to recognize log file rotation and start monitoring from the beginning of the new file.