JavaScript Continuation Support?

Any recommendations for a JavaScript extension to support continuations?

I want to straighten some callbacks for Google Maps (and, yeah, I know Flapjax is another way to do that!). The important part is that I'll be wrapping their API: user code should look like "x = map.getZip(...)" and my wrapper will add in the continuations behind the scenes.

NarrativeJS was early on continuation support, but I don't think it supports dynamic code loading (and I have to trust it wraps gmaps correctly!). More recent approaches (jwacs, strands) seem to build upon it and somehow use JS 1.7 generators for more native support and dynamic code loading, but they seem to add wrapping obligations to callsites that I'm explicitly trying to avoid.

The pay off will be insanely cool :)