I'm just curious, If Borislav Ivanov claimed that he beat Houdini and Rybka 10-0 can't FIDE just make him play them again and he can do it again?
Which brings up another point. If he's playing Houdini's top choice moves, his record against Houdini should be closer to 0-0-10.
For me, the most plausible explanation is the following:
He had (has) an accomplice who follows the game and puts the moves into his computer. The easiest way to do this is either to have an accomplice among the staff of the tournament (somone who has access go all games which will then be shown on screen(s) for the audience), or to hack into such computersystem, or a hidden camera in the tournament hall that shows the moves, and that receives his accomplice.
Further, Ivanov needs to have a very small ear device (loudspeaker), not visible for the people in the hall, so that he will receive the answers of Houdini by his accomplice.
All doable with non-expensive equipment, except perhaps the ear-device.
Anyway, I like the idea of some secret service which wants to test new equipment, and perhaps also the reaction of the chess community.
Did all events in which he played superhuman have cameras over all boards? I agree that for relaying moves back to him, an ear-piece is at least as plausible as foot-feedback, but I also think that for relaying moves to the computer, shoe sensors such as these:
http://health.howstuffworks.com/wellness/diet-fitness/information/nike-ipod1.htm
which he could have retro-fitted in his own shoes, are more plausible than cameras.