import bpy
context = bpy.context
import bmesh
ob = context.object
me = ob.data
bm = bmesh.new()
bm.from_mesh(me)
ret = bmesh.ops.convex_hull(bm, input=bm.verts)

verts = sorted([v for v in ret["geom"]
        if isinstance(v, bmesh.types.BMVert)],
        key = lambda v : v.co.length)

for v in verts[-2:]:
    loc = ob.matrix_world * v.co
    bpy.ops.object.empty_add(location=loc)