^There are only 3-axis of rotation.
In fact there are only 3 axes full stop. Six axis is just a silly term.
Currently the Wii can register acceleration (and thus figure out movement) in all 3 axes (x,y,z)
It can also measure rotation upon 2 of those axes... but it doesn't understand which way the remote is pointing when doing so UNLESS it points on screen.
So currently if you held it up like a joystick (like in SMG) it can register rotation forward/backward or sideways, but it can't register you twisting it.
Similarly Mario Kart won't work if you hold the wheel flat.
The above makes me think it already has a gyroscope in (unless an accelerometer can measure rotation, which I don't think it can) however it's just a simple gyroscope.
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The addon provides a better gyroscope and a (better?) accellerometer in addition. So it can properly figure out it's actual position relative to the sensor bar.
I have no doubt we will see a Johnny Lee video demonstrating this when it comes out.
EDIT: Aha I see, so the accellerometer can work out rotation.... but it is simple and unreliable compared to the gyroscope.
