Sleep tracking has also become a major focus of modern wearable fitness tech. Quality sleep plays a big role in energy, mood, and overall well-being. Wearable devices can estimate how long someone sleeps and may also provide information about sleep stages, nighttime restlessness, and waking patterns. While these measurements are not always perfect, they can still help users notice trends. For example, someone might realize they sleep better on days they exercise earlier, avoid caffeine late in the day, or follow a consistent bedtime routine.