Hand up and down with parrallax effect

I am creating a landing page for a stand alone application (for a school project). When you load the page, you will see an animation that pops up on the iphone in your wrist.

Now I am trying to create it with a parrallax effect. So when you scroll down, the hand will go down, and when you scroll down, it will return to your scroll.

At the moment I have done this with some animations from animate.css, but I want a step into the game to add a parrallax effect.

Here you can see how it looks at the moment http://faces.jorendemaeyer.be

Do you guys know how I can do this?