Related Clues:

• On the lookout
• Like a watchdog
• All-points bulletin
• In a post-caffeine state
• Engaged, in a way
• Absorbed in
• Not at all bored
• Like good guards
• All-points bulletin, e.g.
• Eagle-eyed
• Undivided, as attention
• Standing at the ready
• Sign word that may be followed by an exclamation point
• Shout "heads up!"
• Lost in a good book, say