The last new exhibit of mine at the U.K. Maker Fair was the Dice Game - a game of skill (no luck involved) that revolved around the physical process of sensing which way up a dice was sitting in a small recessed hole.
The full write up, software, schematics and this time Gcode files can be found here:- http://www.thebox.myzen.co.uk/Hardware/Dice_Game.html
It also provides a link to this video:-
Original solution for detecting orientation of the dice :). Did you try any other solutions or did you settle for the Hall sensor right away?
I am wondering if it would be possible to detect orientation of a dice with a few photoresistors/LEDs since most dices (at least in the Netherlands) are white with black dots.
You could do it by embedding six of those very small RFID devices in the dice, the type that are meant to be injected into pets. Also a simply laminated RFID would also do as these are very thin.
You could mount a camera under the dice but that would involve a low resolution video input.