I've asked R. Ari Hart (Hebrew Institude of Riverdale) for guidance in this matter, so I will share here what he told me in the hopes it helps you answer your question.
Devices like these measure the steps you take, and measuring is prohibited on Shabbos. However, since you're not measuring, you let the computer do it, it may be OK. It would be better if you had no way of knowing how many steps you'd taken on Shabbos until Shabbos was over - maybe.
If your pedometer has a watch function, it gives you a leniency, however - you can wear your pedometer as a watch, and the step tracking is incidental. I have a FitBit Flex (no watch function) and am still unsure whether wearing it is kosher on Shabbos. (It probably isn't, but it could be if the developer wrote a Shabbos Mode into the software.)
I doubt that wearing a pedometer as a watch or bracelet would count as carrying - at least, it doesn't for electric watches.
The last thing to consider is whether wearing your pedometer is in the spirit of Shabbos. If you're tempted to check it or fiddle with it, or if it distracts you from Shabbos, then R. Ari advised me to leave it at home, even if there wasn't a definite halakic reason not to wear it.
This consideration is my own: does your pedometer set off any lights or vibrations to tell you you met your goal? Progress lights? Could you set these lights off accidentally e.g. by tapping the device? These would probably violate prohibitions against measuring things and switching lights on/off.