Whisk together the lime gelatin and boiling water in a large bowl until the gelatin dissolves. Pour the mixture into the container of a blender, and add the pear halves and cream cheese. Cover and blend until smooth. Pour back into the bowl, and gently whisk in the whipped topping. Transfer to a mold or serving bowl, cover and refrigerate until firm, at least 4 hours. To unmold, dip the mold briefly into hot tap water to loosen the gelatin, then invert onto a plate.