It's only a little bit harder if you need to communicate in two direction, but - this is chess - you don't need to communicate much data to send out position updates.
Double that if there is two-way communication.
1) it was with a new unknown method/gadget in his body/clothes
2) it was someone from the audience (they switched off the internet broadcasting so anyone outside could not help him any further)
3) the method he used to cheat was destroyed/hidden before the search (eaten, thrown away, etc)
It's a fascinating true story.
A similar device could easily be built for chess computers. Especially since hardware now is much more powerful, and much smaller, and battery technology (while still being lousy) is much better.
What kind of chess computing could you get from, for example, Raspberry Pi? What software would run at reasonable speed on it?
The more obvious approach is to compute the moves on a 'real' computer elsewhere and just transmit the result via some tiny hardware in a shoe or something.
These games were streamed online, so they only needed communication to be one-way (computer to player).