Question about use:
How do you ascertain which direction you point the phone?
Well, I really didn't think anyone would hold it above the model since that is not what you do with the regular scatter dice but you kind of gave me an idea:
What if you where to bring in the camera viewfinder and draw the spinning arrow on it? That would solve your problem. Also add the arrow you are talking about of course so that there will be no discussion

Maybe this is a 2.0 feature.
How to use this application:
Put the phone down as close as you can to where you want to scatter from and double-tap the screen. You shouldn't hold it in your hand unless absolutely necessary. Also a phone usually has a a pretty rectangular shape which you can use to align it with the tables rectangular shape and then there really shouldn't be any discussions... unless playing in a tournament setting I guess.
/Grindah
Automatically Appended Next Post: Having done some stuff with this myself, the compass is more straight forward than the tilt sensors.
Have you seen the new Sensor API? It was probably written by a C-programmer that hates Java. It is horrible to use.