Looks nice! I recently used node to add a web interface to a C++ app myself and got annoyed with the amount of boilerplate code required for passing function arguments (type checking, unboxing, boxing return values) so I started a mechanism for automating it:

https://github.com/pmj/node-method-wrapper

It too is still work in progress, but it works pretty well so far. Note that it currently superficially relies on some node-specific extensions, though they should be pretty easy to remove, in order to use it with V8 alone.