second installment of Iwata Asks (the Wii Fit version), Iwata gets the nitty gritty from the developers of the Balance Board. It's pretty interesting to see what the board could have ended up looking like. Take, for example, the crazy octogan-shaped thing about. Also, whenever reading about a development process, it's almost scary to know all the problems and obstacles that the makers run into.
Of course, the developers prevailed and the Balance Board was born. From Sumo wrestlers to Miyamoto slamming a table, the interview has some nice insight on what it was like to make the unique peripheral. As per usual, click the picture or the "read" link to check it out for yourselves.