I just discovered a cool small application: Duet Display (for mac users only). Just install it on your iPad and the free Mac App on your Macintosh. Then plug the iPad in one USB port of the Mac. You now have a new tactile screen. It is not very large and some sample-sets need good eyes and small fingers, but it works perfectly and without any latency (because of the USB wire). Duet Display can be found in the AppleStore and it is not very expensive.