Working from the WiiBrew description of the MotionPlus protocol I have added support for this to Wiimote.py. I then folded this into pyaxelwii. Pressing button A on the remote reads the last gyro values for centering.
Looking deeper into the Wiimote protocol I found Wiimote.py was not getting the full resolution availalble. We now have 10 bits on x, and 9 bits each on y and z.
I've worked with the author of Pyaxelwii to integrate my changes into the public version. This can be found on the Maemo Garage pyaxelwii pages
I've done a couple of runs with the MotionPlus.
I have made an aluminium bracket with a strong magnet to attach the Wiimote to a railway vehicle.