Proprioception means you can sense the position of your limbs. That is different that what the inner ear provides. You can be blind, deaf, and paralyzed from the neck down, and you will still be able to know when the airplane is starting to descend, even though you will have lost all proprioception.
As someone who flys with pilots they will tell me "You may think the plane is descending but you don't know the plane is descending until the instruments confirm it" :-) One of the fun things they do is fly various patterns that give your inner ear signals that you are doing one thing when the plane is doing something else, its part of a ritual to always check your instruments.
Anyway the notion of extending sense is interesting, and I wonder if anyone has implanted a hall effect sensor (rather than a magnet) and had the eddy current run to the nerve nexus in a finger tip. You would not be able to pick up paper clips but you should be able to 'feel' all sorts of electro-magnetic phenomena.
Integrating with nerves is have-you-a-pet-surgeon territory, and pretty much all of this stuff is done by piercers, or insane amateurs with no respect for their own bodily integrity (see the amazing Lepht Anonym). Few doctors will touch this stuff, for liability or Hippocratic Oath reasons.
The only people I know who _have_ done it are Dr. and Mrs. Warwick, who used it to do nerve-firing-over-IP from New York to Reading.
And your inner ear is fooled because the gloop in the organ-I-can't-remember-the-name-of suffers from inertia, registering false movements (or false lack of movement). Which is why spinning around in a circle for a while makes you dizzy; your ear is registering the movement continuing, your visual cortex is seeing everything staying still, and your brain has no idea how to integrate the two. ",)
I think OP means the vestibular system. Proprioception requires more than balance information, and it's more the sense of knowing where your body parts are relative to each other rather than orientation wrt the external world.
