For decades, hotel guests have been warned about the dangers lurking in their pockets. Keep your room key away from your phone. Don't put it near your credit cards. That magnetic clasp on your purse?

Think back to the last time you checked into a hotel. Chances are, you handed over a credit card for incidentals and watched while the desk attendant typed away on a keyboard for what seemed like ...

Today’s magnetic card key systems are popular with hotels and resorts because they’re flexible and cheap. The door lock systems run off batteries in stand-alone mode — no power or data links are ...