I have looked to port BfX to windows mobile and concluded that the Excel running on it was not able to run the BfX.xll.
How much work Quick Office is I do not know. In BfX the physics part is relatively small, the integration with Excel makes it special. This integration software has to be redone.
My pet project, for which I do not have time, would be the 6DOF. Another one would be controlling the crosshairs of a telescopic sight via a computer in the sight - even compensating for the small movements of the shooter