We think of smartwatches as tools for convenience, tracking our steps, displaying our messages, and monitoring our workouts. But this familiar technology is quietly evolving into something far more profound. The target is one of the most critical challenges in emergency medicine: unwitnessed out-of-hospital cardiac arrest (OHCA).

Few scenarios are more frightening for a patient or family member than a medical emergency. In those moments of crisis, we place our complete trust in the medical team, assuming every responder is flawlessly prepared to perform life-saving procedures. We expect perfection because the stakes are unimaginably high. But how do new staff get the training they need to achieve that level of skill, especially for events that are, thankfully, rare?