Animate with scroll (not on scroll)?

Thanks for a great plugin. I am learning to use it subtly to enhance the sense of dynamic content – it really helps user engagement. There are a couple of effects I would love to achieve and wondered if an update might include them in the future:

Is it possible that an animation could animate with its position in the viewport – as the user scrolls, rather than on scroll. i.e. if they pause the animation pauses. The kind of effect that I would like to achieve is like that used on National Geographica ipad app. As the user scrolls the fade-in starts, but the fade speed depends on the speed of their scroll, stopping if they stop

Also, is it possible to reverse an animation when scrolling or hover is reversed. e.g. fade out on scroll down? Something like fadeInOut or slideInUpDown – with the reverse animation triggered when the scroll is reversed or cursor moves out of hover?

What both of the above achieve is a sense that the effect is controlled by the user rather than triggered as a once-off effect that is ‘done’ to the user.

Just a thought.