I think my sister has an older version of something like this she borrowed from a friend. It goes around her arm and supposedly tracks her activity levels and how many calories she's burned for the day. I guess she inputs her info online and that's how it figures it out for her? She told me once but I wasn't listening. Typical with her. Anywho, she really likes it and is still wearing it and it's been quite a while, since summer, I think.