I have posted a new version of WiimoteLib as a beta for people to play around with the Wii MotionPlus accessory.  Please note that this is not a stable release and should only be used if you wish to mess around with the MotionPlus.  Also note that only C# source code is included in this release as it is not a final build.  Here’s the change log:

v1.8.0.0

• Taiko Drum Master's TaTaCon drum controller supported (Dean Herbert)
• Bare-bones Wii MotionPlus support (wiibrew.org, testing by Tyler Tolley)
• WiimoteTest UI changed to add MotionPlus data
• Please note that the current version is VERY flakey and may not work at all for you.
• Pair your Wiimote, plug in your MotionPlus, call InitializeMotionPlus()
• Extensions plugged into the MotionPlus will give wacky results...not supported...yet!
• Internal changes to perhaps fix some threading issues

So remember, it’s a beta, it may not work for you, and the data you’ll get back from the accessory is just the raw data it provides.  You won’t get real orientation values.

That said, head over to CodePlex and give it a try!