genmon plugin for the Xfce panel

The genmon plugin is a 'generic monitor' plugin that cyclically
spawns a script or program and captures its output, then displays the
resulting string in the panel.  It can be used to display a picture,
a bar, tooltip, and/or a button, so it can be used to display various
information about the system, such as temperature, processor speed,
battery level, etcetera...