FrozenCow has released Wii Device Library v1.1 :

Wii Device Library is a cross platform C# class library that provides an interface to various Wii related devices, like the Wiimote, Classic Controller, Nunchuk and Balance Board.

Itís possible to use Wii devices like the Wiimote or Balance Board with your computer. All you need besides one of these devices is some kind of bluetooth device. This could either be a bluetooth dongle or bluetooth built into your pc or laptop.

When using the Wii Device Library you donít have to worry about all the bluetooth stuff, you can just access your device of choice through a simple and intuitive interface. Also new Wii devices and extensions can be implemented by this interface without recompiling Wii Device Library.

Another nice feature is the ability to scan for Wii devices through bluetooth and connect to them when they are available. This makes it possible to automatically connect to Wii devices when they are syncing. It uses the libraries of several bluetooth stacks to scan, connect and communicate with the Wii devices. Also this part of the library can be extended with support for more bluetooth stacks and/or operating systems.

Supported Wii devices

Wiimote
Nunchuk
Classic Controller
Guitar
Balance Board
Supported bluetooth stacks

Microsoft bluetooth
BlueSoleil
BlueZ
Features

A simple and intuitive programming interface.
The ability to scan and connect to Wii devices.
Wiimote extension support with a wide range of implemented extensions.
Support for multiple stacks.
The ability to extend the library to support more Wiimote extensions, devices and stacks.

http://wiibrew.org/wiki/Wii_Device_Library