It looks like the Wii Motion Plus has been hacked so you can read the data via an Arduino. The build only requires about $4 in parts. Now that’s cheap! Check out the website for the schematics, code, and more information.
Alright, one great aspect about the Wii Motion Plus is its pass through port for other extension controllers such as the nunchuck. Unfortunately, no one has been able to read both an active motion plus and any other controller at the same time because they are all on the same I2C address(smooth nintendo). This is creates a large hurdle to people like myself who bought the WM+ to create a low cost IMU with it and the accelerometer in the nunchuck. After a good deal of digging and very little luck, I did find a way to use both at the same time(though not through the pass through port). And best of all its cheap!
In the Maker Shed: