I have been using Stepz on my iPhonecfor a year. I really enjoy the way it tracks my progress and achievements. The programmers need to tweak it to provide more motivation, such as recognition for hitting 1,000,000 steps, 1,500,000 steps, etc. And there is too much distance between some of the mystery achievements - 200 miles should be the limit - and these milestones with 300 and 700 miles to the next milestone need to be redone with more intermediate goals.
Overall, its great and I highly recommend it.
Goldylox99 about Stepz - Step Counter & Tracker