The Wii Remote, informally known as Wiimote, is a Human-Interface Device (HID) that communicates through Bluetooth protocol. The controller consists of the following sensors and features:
The Wiimote also has an EEPROM memory and registers, both accessible through read/write operations. Communications with a Wiimote device are performed by output and input reports. The former allow to command the controller, to submit a request, or to send data. The latter represent reply to requests or status reports. For an overview of the device and its functionality, you can refer to Wikipedia, while for a technical description you can have a look at WiiBrew.