Creating services

Hi people.
I'm trying to do tools to simplify testing and check "quality" of packages before saving them (thanks Steph and Lucas your recommendations on how to do code coverage save me a lot of work).
I want to do some simple services:
   - a menu option to run unit tests of a category
   - a menu option to browse unit test/tested class
   - a menu option to auto categorize uncategorized method (so the AutomaticMethodCategorizer doesn't have to overwrite the Browser class)

And I trying to figure out how to make a new "service", but I can't figure out what is the correct way to do that.

I must create a subclass of ServiceProvider and implement #providedCategories?
If this is the case, what is the meaning of the symbol array of arrays returned by this method?

small critic/question follows:
Why #providedCategories returns an array of symbols and not an object that reifies the provided categories?