Outdoor warning sirens have long been the primary emergency notification system utilized by emergency managers to warn their citizens about severe weather threats or other community hazards. They are based on the infrastructure and philosophy of civil defense sirens and are often distributed throughout communities based on budgetary availability and population density. Unfortunately, technology, human behavior, and social science have reached the point where sirens may no longer be capable of serving as the primary system for emergency warnings. This article evaluates and contrasts the cost versus benefit of various emergency warning strategies with a particular focus on the rise of systems with greater portability and mobility.