Will you all READ? You don't drag your fingers over the keyboard. You perform gestures ABOVE the keyboard and the camera picks them up. Horrible idea, but it is still what is being proposed in the article.
What makes you so sure of this? I've re-read the article and it still sounds to me like you drag your finger across the keyboard.
It sounds just like the mini keyboard for the PS3 actually, which works in that way. It's not very effective tbh.