Some recent documentation has surfaced detailing the Wii's controller and how much of the inards work exactly...
~ Uses 2 AA batteries.
~ 30-60 hour battery life depending on type of use.
~ Communicates with Wii console via 2.4 GHz Bluetooth signal.
~ Contains 6KB of non-volatile memory for an unknown purpose.
~ SYNCHRO button on console and remote tell system which controllers are working with it.
~ A shortcut for SYNCHRO is holding the 1 & 2 buttons.
~ Each controller is given a wireless ID number.
~ All buttons are digital.
~ The 20cm long Sensor Bar has a sensor on each end which interacts with Wii-mote.
~ LEDs on WiiMote used to indicate battery life as well as which player it corresponds to.
~ Halogen lamps, fluorescent lights, and light from plastic or mirrors can affect the Wii's sensors.
~ To combat this, the Wii-mote needs to first register the coordinates of the two sensors on the sensor bar
Source:
Nwizard