there were a few. Do you have a specific question in mind? I use the Fitbit myself and just enjoy it for the fun of it.
I also happen to run a walking program where everybody got a step counter when they signed up. It is a less sophisticated model but it can be uploaded to a computer, and the user can also add more information to their profile. It is quite amazing for me to see how motivating this little device is for the senior group. People love to see numbers; it makes things more tangible.