Originally Posted by Feynman
It almost seems plausible as the same size device, same interface has surfaced by different users, showing different apps....
However, there's a really problematical shadow being cast by the left hand (hard to get a shadow on a backlit surface).
You can do this by having someone run some rehearsed gestures on a blue surfaced tablet mockup, then lay in your animation, timed to match the finger hits, after the fact. Motion tracking takes care of the "device" moving around.
I think people underestimate how wide spread motion tracking software has become. Check out some of the "handheld camcorder" footage of UFOs on You Tube. There's something about CG put into a shaky setting that really sells the illusion.