It’s noisy on the beach, and you want to call your kids back (you want to go home, or they have gone too far in the water, etc.)
Have a wristband that strongly vibrates when you “call it” using a phone app or a dedicated transmitter “button.”
You can watch your kids and stay calm without moving a finger.
Have a binocular rental service at the beach. Watch your kids (or anyone else you find interesting), while staying comfortably in your comfortable chair at the beach.