They wouldn't turn it off - but they'd have no need to refer to it if the ball made the onion bag bulge, surely?
It doesn't work on a referral system, the watch Buzzes when the ball goes in. If the watch doesn't buzz it's not a goal or at the very least the referee stops the game to find out why his watch is broken.
I hope it vibrates enough that he notices; my phone vibrates in my pocket and I barely feel it. If the ref is running, he might not feel it go off. I recommend replacing the vibrating mechanism with a small but sharp needle that jabs them in the wrist when a goal goes in.
I agree, with just enough sedative to temporarily paralyze the ref so that he drops to the floor. That way no one is in doubt.
how many times a year is it needed in a season of the Prem ? 3 or 4 ? i cant see there being a problem , until the first time its needed theres a malfunction and the designers are promptly burned at the stake by the Daily Mirror and Sky