To perform an action when the user moves multiple fingers on the map, override the onGestureStart/onGestureChange/onGestureEnd methods as required. The link above provides more details on the content of the received events. The gesture events don't provide the actual touch locations, so if you need this information it may be necessary to override additional methods such as onTouchMove.
For a good example of a control that processes gestures, look at the code for the mobileViewer.PinchZoom class.