Nice project. Check also some of the i18n classes in Google's Closure package (http://code.google.com/closure/library/), for more comprehensive routines and support for almost any currency.
Yeah, that could work actually - I've purposefully left everything to do with symbols (apart from the standard dollar sign) up to the developer, to avoid bloat, but I can see a use case for the most common ones (along with default formatting for said symbols)