with half an eye on (something/someone)

have/keep half an eye on (something/someone) - to watch something or someone without giving them all your attention.

I ate my lunch with half an eye on the clock to make sure I didn't miss my train.

• catch the wave
• catch up on
• catch up on something
• catch with fingers in the till
• catch with hand in the till
• catch with their fingers in the till
• catch with their hand in the till
• catch you later
• catch you napping
• catch your breath
• catch your death!
• catch your death of cold!
• cat got tongue
• cat got your tongue
• cattle market
• catty-corner
• caught in the crossfire
• caught in the middle
• caught short
• caught up in
• caught up in something
• caught with pants down
• caught with your pants down
• cause a stir
• cause celebre