[derac]

You could play in a Faraday cage, use an SDR and check for weird radio signals, and other steps. Some of this would only really be feasible at the highest levels, but that's where going to those lengths is needed.

[rurban]

We just had a project on HN with the stockfish engine and sensors both in the shoe. No radio signals whatsoever needed.

[derac]

The other steps would have to include thoroughly checking clothing.

[FartyMcFarter]

That just means cheaters will have to embed the devices in their body.

[derac]

Airport body scanners?