Ignore held finger

[ET]

I let my 2.5 year old play with Zebra Paint, and she seemed to enjoy
it, even though her understanding of how to use it isn't perfect. One
thing I noticed where she had a problem is that she holds the phone in
such a way that her finger is on the glass. As a result the other
hand's finger which she uses for painting isn't registering.

Since the phone is multi-touch (as the majority of Android devices
are), it'd be nice if a static finger held like this could be ignored,
and the second finger function as if the first isn't touching the
display.