well, if you put two fingers on your MBP trackpad and move down or up only one of them, it scrolls slowly. If you move both, it scrolls faster. I don't know how they achieve this and what kind of hardware or software underlies this system. If the MBP trackpad can detect the the position of two fingers, you can do anything through the magic of software. It's quite basic math actually to pull off the rotation and all those movements which i don't know why people are so amazed by.
