osgGA. My approach is to bundle all touchpoints into one custom data
structure which is attached to an GUIEventAdapter.
The current approach simulates a moving mouse for the first touch-point,
so basic manipulators do work, sort of.
I created a MultiTouchTrackballManipulator-class, one touch-point does
rotate the view, two touch-points pan and zoom the view as known from
the iphone or other similar multi-touch-devices. A double-tap (similar
to a double-click) resets the manipulator to its home-position.
The multi-touch-trackball-implementation is not the best, see it as a
first starting point. (there's a demo-video at http://vimeo.com/15017377 )"