A Python script which runs itself inside Blender upon being run from the command line. Passes through command line arguments.

blender-script.py

#!/usr/bin/env python3

import sys

try:
    import bpy
except ImportError:
    print('Running myself inside Blender')
    import subprocess
    exit(subprocess.call(['blender', '--background', '--python', __file__, '--'] + sys.argv))


print('I am running in blender')

argv = sys.argv
argv = argv[argv.index("--") + 1:]  # get all args after "--"

print(argv)

This is awesome, thank you so much!