Sorry if there's already a thread for this...I looked and found them for Wii Fit and Wii Fit Plus but not Wii Active.
I have the Wii Fit Plus, and I enjoy the games and use it to track my progress. I don't get much of a work out from it, but it's better than sitting on my bum for 30 min. My boyfriend bought me the Wii Active for an early Christmas present, and I've played it for a few days and I'm really pleased with it.
It comes with a leg band that you put the numchuck in so it tracks your lower body movement and also a resistance band (the band is pretty weak, I used my own). There are a few different ways that you can play...I haven't really looked at all of them, I've just done the 30-day Challenge. It's about a 25-30 min workout that goes through cardio to weights. The running is much more realistic than the Wii Fit, you're running in place not on the balance board.
Like I said, I've only done two days, but I've worked up a good sweat each day and I feel it in the morning. For anybody looking for more of a challenge on their Wii, I'd definitely suggest this game.