My sister bought me a fitbit flex and I love it. We went to WDW last week and walked just short of 100 miles over the course of the week. It was fun to see those steps add up every day.
The fitbit did fine at the waterparks, too. I was a little worried about the wave pool and Crush n Gusher at Typhoon Lagoon, but the fitbit did fine. I wish it would count swimming time as steps though!
I had to charge it more last week than in my usual weeks where I average about 10,000 to 20,000 steps a day.
Hopefully you all can see it in action at WDW on your own trips!