[AKrumbach]

A search on Google turns up this Common Lisp code, which appears to define a number of SI units (both base and derived) in the sort of manner described.

http://www-ksl.stanford.edu/knowledge-sharing/lib/unit-conve...

Given the way this appears to be defining some sort of class-based hierarchy, with the correct type requirements this code should perform exactly the sort of unit/type checking the grandparent post wanted, but I didn't go digging into the rest of the project files to confirm this code defined things in the correct manner for that to work.