Depends on the game type and cheating type. If blitz type game where players have <5 minutes to decide a move, then yes, delayed broadcast might be effective.

Depends on the game type and cheating type. If blitz type game where players have <5 minutes to decide a move, then yes, delayed broadcast might be effective. Other game types allow for >5 minutes per move so tape delay would be ineffective since cheater could just stall. Cheating type also matters. There's external help (friend in the audience communicating 1 or more bits of information via auditory, optical, radio, or some other signal), and there's also internal help (raspberry pi zero + battery and pressure sensor embedded in your shoe or something). There are so many ways to cheat that it's hard to enumerate all of them let alone prevent all of them.