There was a person who got caught cheating a while ago by using a modified shoe and having a 3rd party send moves through the shoe, it was a much lower level thing than this, though. I'm sure if you were clever enough you could make something that eliminates the need for a third party now adays. Just like excessive bathroom breaks will get you kicked out of a tourney.
Still no 'smoking gun'
I have been curiously watching this unfold over the past month.
I think it will eventually come out that he is a cheater, not just online but also "over the board" ie in person.
He has many games in the past few years where his efficiency score matches 100% with the latest top chess engines (Stockfish), including some games going into 30+ moves.
Not Fischer, Carlsen, nor Kasparov have ever had a game where they score 100%, and this guys has had multiple in a few years?
That extreme statistical improbability coupled with his inability to explain his reasoning behind specific moves in matches he just played (one interviewer has him simply saying "the chess speaks for itself" then walking off) is enough for me.