Comment by jandrewrogers

This is unlikely to be a shaped charge, there is not enough space. High explosives are inherently directional depending on the geometry of the explosive and point of detonation. As a practical matter of fitting explosives into a pager, I would expect most of the explosion to be directed perpendicular to the face of the pager in both directions. In almost all cases, carrying or using the pager would put the person directly on the main axis.