15 minute delay doesn’t seem sufficient in a classical game. Spending 15 minutes on one crucial move is common and wouldn’t raise suspicion.

Give a little squeeze at the start of your turn, to indicate that you wish to request the next engine move, then sit there for 15 minutes appearing deep in thought until the answer is beamed to your behind.

Alternatively the device could stream all the moves with the move number encoded, so it could be entirely unidirectional and you wouldn’t need an input method. Just wait 15 minutes for the next move.

Typically not, though they did introduce one in the St Louis tournament after Carlsen withdrew.

I wouldn't be surprised if they became more common going forwards.

Agreed.

There are many legal reasons that they could not perform a body search for anal cheating devices, butt more importantly: human perseverance has shown that some communication devices will always be able to stay hidden...no matter how invasive the search.

You could fix the communication by putting participants in something like a Faraday cage, or lining the walls with lead etc.

However, if someone puts the actual chess computer inside their body, even those measures won't help.

It would complicate the buttocol a bit but one could imagine having the engine predict the opponent next moves and propose different responses to them: if e5f4, then e3f4 – if c7c5 then ...

Why? You can just send the next move after the opponent made theirs.

How do suggest to send a move via Buttplug?

Anal sphincter contraction sensor...

https://www.e-arm.org/journal/view.php?number=1548

The same way it's doing it now.

Squeeze?