The more we understand about the importance of sleep, the more we try to improve our sleep — making apps that claim to track sleep using smartwatches and other devices increasingly popular. But the technology is still new, and its effectiveness is not fully understood. A study by scientists in Norway shows that, while some users find their sleep improves, people with insomnia symptoms are more likely to experience stress and other negative effects. If your sleep is already poor, using an app to fix it could make things worse.