Niib, for "notes de l'IUT informatique de Bordeaux" (marks of Bordeaux's Computer Science University Institute of Technology) is a small extension that compute the marks average on the marks webpage.
This extension works on Firefox and Chrome.
It compute the average of the modules, the average of the UE (containing several modules) and the general average. It also calculates bonus points obtained for participation in clubs.
Here is a little comparison without and with the extension: