I would say, cars most definitely yes. And we should not only consider concrete objects even. There's really no principal difference in the way we learn to operate the character in a video game, or an internet browser, from how we learn to walk with our legs and body - it's prediction and feedback just thee same. That's the plasticity of the brain.
I think it's a little misleading to talk about "temporary body parts" however, as if there are some distinct conditions for when a tool is like a part of your body and when it's simply a tool we learn intimately.
"Woa, is this hand really a part of me??"
The neocortex really is an amazingly extended phenotype.
> there are some distinct conditions for when a tool
> is like a part of your body and when it's simply a tool
> we learn intimately.
Perhaps these are just different points along a continuum-- all tools (and limbs) are integrated into the body schema to varying degrees. Consider that dancers learn to exert far more exquisite control over their movements than most people do. Another example: a large portion of strength training gains are not simply due to muscle hypertrophy, but to the motor system learning how to recruit the muscles in more coordinated and controlled ways.
Edit: On re-read, it looks like we are agreeing with each other. :-)
I would guess it does go as far as any whehicle you're driving and can "sense" its location in 3D space, i.e. know when it's about to bump something. That would make you very good at parallel parking.
Not me though, I suck at sensing where exactly the car ends, either that or my car randomly changes size throughout the week.
I'd argue they become an unconscious synapse to the tools we perceive in the machine. Avatars in games, the cursor in editors, these are what we feel as the extensions of our will in their environments.
