Related Clues:

• Gives a heads-up
• Sirens
• Cautionary signals
• Cautions
• Gives a heads up
• Red lights and flares
• Foghorn blasts, e.g.
• Notifies
• Beeps, maybe
• Red ones are quite urgent
• Security concerns
• Gives a heads-up to
• Sounds the alarm
• ''Heads up!'' and others
• "Fore!" and "Duck!"