I bought a fitbit zip for my wife and she's been wearing it daily.

We like it better than the runkeeper on the phone bc there are many times during the day when the phone is not "on your person". For example, getting up to go to the printer, you leave your phone at the desk. However, you're still taking steps and burning calories.

I think the fitbit web site / app could be better with the types of badges / encouragement but thats just my 0.02.