Yes, I'm constantly referring to my "phone" as my "brain's third hemisphere". It makes people chuckle but no one stops at that joke. It's completely "in the culture".
My late friend Hugh Daniel used to refer to his Bihn's backpack as his "LSD", for "Life Support Device". Like when we were leaving the house he'd shout "Oh no, I forgot my LSD! I'll be right back!" then run back in and fetch his backpack.
