unless your game-concept isn't totally useless without multitouch, you should still support singletouch somehow.
The only thing in your code that changes when you use the MultiTouchController (instead of the default default SingleTouchController) is that the method getPointerID() of the TouchEvent will return a different ID for each finger. Thats a little different from the way Android itself handles MultiTouch, by squeezing all fingers into on MotionEvent.
Basically if you start your implementation by remembering the "activePointerID" you are on the safe side for both Single and MultiTouch. Its like associating the (active)PointerID when the object the finger goes down (ACTION_DOWN) on an object and only reacting MOVE/UP-Actions of TouchEvents where the PointerID is the same as the activePointerID.
This is how the OnScreenControls do it and it seems to work very well.
See: http://code.google.com/p/andengine/sour ... ntrol.java