Yesterday, I managed to pick up the Wii Fit from JB Hi-Fi for $119 AU (EB Games were selling it for $149 AU - How rude !) and boy is it great. Very simple to use and the exercises/training games are fun to do -- I was completely buggered after doing the Short Jog :)
It's a great way to track your BMI and Weight too, as every day when you do a Body Test, it calculates these measurements and graphs your progress. You can even set goals to work towards.
Great fun and losing weight at the same time. My wife loves the Hula Hoop-ing and I'm a bit of a step master ;)