Wii Fit nuts who want to add some cardio/weight training to their Wii gaming/workouts should check out the Riiflex Dumbbells. The Wii dumbbells slide over the Wii-mote and Nunchuk controller adding a full 2 pounds for each hand.
The Riiflex Wii Dumbbells are made from strong polycarbonate with a soft rubber cover (for better grip) so that you don't end up throwing your heavier Wii controller through the TV.
The 2-pound Riiflex Wii dumbbells are available now for $29.99 here. Riiflex plans on releasing a 4 pound set in the future.
The company also has plans to release 4-pound (1.8kg) dumbbells at some point in the future so you better get into training now.