Filter out input of wrist

[peteruithoven]

When users draw using a stylus they sometimes put their wrist on the screen. This can result in multiple lines to the bottom right of the screen.
Can we filter these out somehow?

Maybe when a difference between a previous and new point is to big we ignore it? This could disable the straight line drawing trick (using multiple fingers).
Can we double check whether input outside of the drawing field is ignored?