I have a fitbit zip also. Love it. I clip it to the center of my bra and I don;t see how it could ever fall off. I also clip it to my PJ's when I put them on. I want credit for every step. It is advertized as water resistant, that sweat won't harm it. I can verify that it works. I work in a school with no AC and it stands up to sweat. Also I accidently ran it through the washing machine once. I am really surprised at the number of steps I get in during a typical day, without any added exercise. I am all over the school in different classrooms. I usually have about 7000 steps in by the time i get home.