The most common and largely practical way to locate travelers in a crisis is to look at who intended to travel to the area and ping them. Credit card swipe data is another way follow an employee's path. Potentially even more effective, GPS-based tracking is challenged by privacy concerns and battery drain. However, a relatively new crop of providers is trying to change that. They obscure the location data until it's needed, streamline messaging and assume that when people . . .

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