Hmm... for a serious workout, I'm still waiting for nintendo to release extra 'equipment'.
For instance, they are already developing a new 'light-gun', in which the Wiimote can be inserted. Also a special Tennisracket and Golfclub can be bought to insert the Wiimote into.
When does Nintendo start making special weights that we can insert the Wiimote into. These should be in different classes, for instance 1, 2, 5 kilograms.
It would make Wii Sports a real workout.