First I want to assure everyone that I asked this question to a proper halakhic authority and will proceed with my actions based on his answer. I am asking it here as well because I think it is an interesting question.
Can one wear a fitness tracker on shabbat if it is worn as a watch? The device would always show the time, but it would be collecting data in the background. Then after shabbat use the data that the device collected for whatever abstract personal interest a person might have with the data.
The Garmin Vivofit is the specific device I am speaking about.