UK Daily Mail 
September 18, 2013
They say that necessity is the mother of all invention and need is never greater than at a time of war.
So that may account for the unconventional method being used by these Syrian rebels to aim mortar shells.
Members of the ‘Ansar Dimachk’ Brigade, which operates under the Free Syrian Army, were snapped on September 15 using the tablet computer to help fire a homemade mortar towards a battlefront in Jobar, a suburb of Damascus.
Twitter speculation suggests that the soldiers might be using a spirit level application to determine the angle of fire, a key measurement which affects how far the shell will travel.