Fitbit

Many of the digital devices in our lives encourage couch-potatoism. But Fitbit’s wearable activity trackers challenge our modern-day inertia, lacing into our La-Z-Boy ways with every counted step. Studies show the wristbands boost the physical activity of just about anyone they’re slapped on—including recess-going children, post-menopausal women, and sedentary adults. That makes them a promising intervention to fight obesity and increase basic fitness—and explains why companies like Diageo and BP give them to employees, and some insurers (see No. 17 on our list) are using them in health plans. Fitbit data have also proved to be a strong predictor of which patients, after their hospital discharge, are likely to have complications and be readmitted.