If you're nervous that your attendees might keel over after a ride on Disney's Space Mountain (that famous in-the-dark roller-coaster experience), you might rest a little easier knowing that Orlando, Florida's mega-park is strengthening its emergency response system with an army of automated external defibrillators.

An AED is a portable lifesaving device that can jump-start a heart in cardiac arrest by sending an electric shock to interrupt a heart malfunction called ventricular fibrillation. Walt Disney World Resort is deploying approximately 500 of the laptop-computer-size units across the 47-acre resort by June, making it one of the largest private installations in the United States. The units are intended for use by nonmedical professionals, and Disney “cast members” are being trained.