I tried making Graal work on my Ipad, as I wanted to watch tv and play graal at the same time.
This was the result:
http://www.youtube.com/watch?v=mYUwxKAcshk
It was ok and there wasn't any lag, but it turns out its funner just to play on the pc.
To achieve this I used splashtop 2 app and the addon or whatever its called that lets you add programmable buttons onto the screen. Its not free so it kinda sucks, but it works.
It also requires you to have graal running on your pc.