The Oura ring analyses sleep quality, phases of recovery and activity by measuring physiological signals. Insights and guidance provided by the accompanying app help users learn to improve their sleep and daily rhythms for better performance. On the face of it, the ring appears as an elegant, modern piece of jewellery – the technology remains noiseless and concealed in the interior. It can be worn non-stop, is water resistant to 150 metres, and the battery lasts up to one week.