A surgically planted bomb? That would take some skill and a fair degree of bravery from the surgeon. Also its inaccessible, and the trigger mechanisms may be very difficult.
Surgically implanted bombs arent impossible but are more likely to be the product of a paranoid schizophrenic's thought mechanisms.
Body packing, however, is a completely different thing and is entirely possible and feasible for concealing a bomb and gaining access during flight.