[eru]

You could stick the computer in your shoe, like the submission suggests?

Or you could swallow a buzzer? The input could come from someone who watches the board from afar?

[whimsicalism]

They metal detected & RF frequency detect before the round 4 match.

[FartyMcFarter]

RF detection before a match seems useless, unless the device is in constant communication.

I don't know enough about those devices and metal detectors to be able to tell whether that's effective mitigation. Could one make a device small enough to be hard to detect?