Something I've wanted to do for ages was to make my own 3D Wii MotionPlus demo! I made it in Python with cwiid and Soya3D. So I did it.
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Soya is awesome! It has a built in collision detection library (and you can access the ODE physics engine) and a 3D GUI library called Pudding (Soya Pudding, geddit?) and a network gaming engine called Tofu. And it talks to Blender/3DS max/old school quake models and maps nicely.
In this house, we obey the laws of thermodynamics physics!
That's not to say it hasn't been hard.
For one, the catepillar had the ability to roll onto itself and then push itself into the sky - which it does within a minute of the simulation starting. Now it just curls into a ball instead and then snaps out of it.
Thanks to the hackery that Nintendo did to jam the MotionPlus onto the bottom of the wiimote, I can't seem to get data out of an attached Nunchuk (although it's meant to be possible).
The MotionPlus needs alot of recalibration but you can trick players into doing it when they click on things. And I-Am-Not-A-Geometry-Expert. I have enough trouble rotating things in 2d space with a fixed axis... Soya has Subworlds on each Character model with their own 3d axis.