For those who have never used Fvwm, it is a modular window manager - modules used to create the desktop GUI are loaded in the ~/.fvwm/config file, or started from the menu (Enlightenment - e16 and e19 - were forked/derived from Fvwm so if you have used either, you get the idea). The typical modules to load are FvwmPager and FvwmIconMan for pager and icon (taskbar-type) management. An IconBox can also be used for icons on the desktop. FvwwmButtons can be used to create your typical panel.
One module, that get overlooked a lot (IMO anyway) is FvwmScript. This module allows the user to build graphical applications that can be used as desktop widgets. FvwmScript uses it's own particular programing language, and each script consists of 5 parts so writing one from scratch would be a bit difficult. Easy enough to find some existing scripts
at the Fvwm forum page, or some of the sites
that have Fvwm themes like box-look.org..
I grabbed a few that had the information I wanted and tweaked them to my liking. After messing around came up with:
direct linkdesktop is almost all Fvwm modules - only 3rd party app is stalonetray for the system tray; not a significant hit to resources running scripts for all the system resource information.
As with all Fvwm modules, the man page is pretty extensive; but still best to get an existing script and sort it out.