This project is toward the implementation of a decent Units system in FreeCAD. It follows the rules of the Getting things done process. The projects are collected in the Development roadmap.
This is a software development project aimed to implement a Unit-system framework into FreeCAD.
The development steps are planed here (Next actions) and tracked in the Issue tracking system to get a well formed change log: Issue tracker
It will enable FreeCAD to handle wired measurement systems, like the imperial system, and complex compound SI units. Also handle the import/export formats which are able to transport Units (like STEP). And allow scaling based on assumptions of Units (mm->m, m->in).
Lots of discussion was done here: http://forum.freecadweb.org/viewtopic.php?f=10&t=1616
And lot of information you'll find in the Units article.
Upgrading the parser to handle and generate signatures as discussed in the Units article.
Changing the properties form e.g. PropertyLength to PropertyUntit with a unit signature.
Eventually a property editor for the PropertyUntit.