IIRC, you reduce the tolerance value (an options you can pass to headroom) it will work on iOS also, it just isn't quite as sensitive as it should be. I'm waiting for my development iPhone to charge so I can confirm this. I'll report back :)
Perhaps you could make it work (albeit less gracefully) in iOS by reconciling the header visibility state once "touchend" finally gets fired though? Assuming "touchstart" gets fired as you'd expect, you can do a bit of manual calculation to determine if the y-position changed enough to warrant header hide/show.
However, now that I have an iOS device (which is still charging!), I should spend some time seeing if I can get it to work better there. I'll look at various touch events as you suggest. Currently it only listens to the scroll event
Edit: version 4.2 Android Browser. I scrolled a good enough distance down the page.