This actually tracks as the Wii Balance Boards needs good sensors to accurately sense how you are shifting your weight. I imagine they use better and more weight sensors than your average bathroom scale.

I have a "smart" scale from Polar that fortunately could be used as a regular dumb scale. I think Polar is really great in this regard. Their watches and other equipment can be used without syncing or connecting to their cloud, but the cloud does provide you extra value if you want to use it.