I only used a pedometer that measures the number of steps you've taken. The ideal ones are the ones that allow you to enter the measurements of your strides. I found that they're quite accurate and off only when you're doing something besides directly walking but indirectly walking (if that makes any sense at all). For example, let's say I'm walking to work from my car, I count the number of steps - yeah dorky I know - and it's accurate. However, when I'm standing in line at like say to eat, I found that it's very inaccurate since it's not measuring the steps you're taking since you move one leg, and not the other.