WatchKit Complications

WatchKit Complications are glanceable data displays on Apple Watch watch faces. Instead of launching a full app, users see relevant information (weather, heart rate, stock prices, reminders, fitness activity) at a glance on their watch face. Complications use Apple's ClockKit and WidgetKit frameworks to render data with extreme efficiency—strict memory budgets, CPU limits, and battery constraints. Designing and implementing complications requires understanding watchOS lifecycle, background refresh, and Apple's strict review guidelines. Complications are high-value: users glance at watch faces dozens of times daily; a well-designed complication has massive engagement.