This is a Screenlet (a linux desktop widget) which indicates CPU load with rotating polyhedra. The higher the CPU load the faster the shape spins (or slower, if you configure it that way). It’s available for download on GNOME-Look.org or directly here.
Screenlets are Python modules with Cairo doing the rendering. Cairo can only render 2-dimensional polygons, arcs, lines, etc., so everything 3D about Gyrometer is implemented from the ground up, from 3D vectors to perspective transformation and lighting. I’m sure there are available libraries and modules to do most of that work, but I didn’t want a Screenlet that had extra dependencies, and I wanted to get to know some of the real basics of 3D graphics. I learned quite a bit about Python, as well.