New study suggests the devices can help people become more active. In the study, women who wore a Fitbit saw a boost in their physical activity over a four-month period.  study involved about 50 women in their 50s and 60s who were overweight and generally not very active. About half of these women were given a Fitbit One, a fitness tracker that clips to a person's waistband and tracks a number of metrics: how many steps they take, the total distance they move, the number of floors they climb, the calories they burn, and the total number of minutes during the day that they are active.