Hi . My wife, Kelly Mack (a contributor here), also uses the Visible app. In fact, she started with the free version, but now has the wearable device. She finds it very helpful. While she says (I'm picking her brain right now) the wearable device isn't 100% necessary, she finds it helpful for pacing throughout the day, finding trends, and where her energy is being spent. She definitely feels it is pretty accurate as a predictor of her state/energy levels for the day. She says she could go on/discuss this for hours, but I'll simply ask if there are other questions you might have about her experience. Best, Richard (Team Member)