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

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 ;)