Now on its third generation, the Oura Ring is a great alternative to wrist-based health trackers, and of particular interest to those with an affinity for traditional timepieces. Its sensors detect heart rate, temperature, and oxygen levels, allowing it to track activity, fitness, sleep, recovery, and overall health. Yet it's always had a somewhat oddly faceted shape — until now. The Horizon model places all the same technology in a perfectly round, water-resistant, PVD-coated titanium band, with seven days of battery life and compatibility with Apple Health, Google Fit, Strava, and Natural Cycles. Available in five colors.