[DSMan195276]

The Wii Classic Controller is wired. The port on the front of this console is the same port on the bottom of a Wii Remote, which makes it pseudo-wireless in a way, but there's no Wii Remote in this case so it is just wired.

[happycube]

Yup, it's I2C with a 1394-ish connector (which makers have taken advantage of before), so it is very easy to implement... with the added side benefit of selling a few of the standalone controllers for Wii[U] virtual console use.

The console itself is probably a simple ARM chip - the BCM2835 in the first-gen Raspberry Pi would work perfectly, among tons of other possible SoC's. It will probably be under a plastic blob, but someone will find out sooner or later ;)