Related Clues:

• Tesla smash
• Radiohead "No ___ and no surprises"
• Cautions, reservations
• "Heads up!" and the like
• Noisy types with gangster capable of releasing firepower
• They might range from green to red
• Smartphone conveniences
• Messages to mailing-list members
• Traffic app notifications
• Clocks that wake sleepers
• Civil defense sirens, e.g
• Danger signs for revolutionaries covering up slump
• Morning buzzers
• Some iPhone notifications
• The stars in a number of versions of The Omen perhaps