I don't think there's much evidence of that. What we were trying to do was experiment just to measure children's everyday activity. We didn't want them to do more exercise because they were wearing the monitors, because that would rather upset the experiment.
I'm afraid I don't really know the answer to your question on whether wearing a pedometer helps. A lot of free pedometers are given out in all sorts of places, sometimes by people selling food. They certainly do seem to work in the short term in terms of encouraging children to run around a bit more, but I'm not sure there is much evidence of the long-term effects of them having much benefit.
Maybe my colleagues know better.