The video and models are being rendered on top of the camera view, which is the video background in Vuforia apps. This is why they are drawn over your hand. You can use VirtualButtons to recognize where your hand is on the target and affect the augmentation accordingly, but VB's are rectangular and so you wouldn't be able to isolate a region that follows the contour of your hand or finger accurately.

This is not easy to do at all. Perhaps even impossible with the current state of technology. Think about it. The app needs to know the 3d shape of your hand and what it's location and rotation is in 3d space to be able to occlude the AR content. Perhaps you can strap the depth camera of the MS Kinect to your phone or tablet, somehow stream it's data into the app, and use that as an occlusion mask.

I think it is safe to say that this feature is not going to happen in the next couple of years at least.

Thank you for this information :).

Thanks for the tip.

i think this will be resolve more easy with a skin recognition, and there a lot of papers of that subject, i think this is what sony is using for his wonder book when the kid put the hand over the book and when he holds the ps move and put a wand model but leaves the hand