On March 10, 2006 Nintendo filed a patent for an “Accelerometer-based controller” in Japan, which is now registered on the US Patent and Trademark database. I wont bore you with the technical details because we know what it’s for, the Wii remote.
On further perusal, the patent figures have some interesting tidbits. One sketch shows Mario playing tennis, which we know from a previous GDC was of the original concepts that became Wii Sports Tennis. Another figure shows the Wii remote linked to a Gamecube console via a Wavebird-like adapter.
Images courtesy of the USPTO / Nintendo.