I just read an article, complete with pictures of the way the guy had his electronics rigged, on Chessbase. A 19-year-old 1500-player beat a GM in a tournament in New Delhi. His opponent noticed the guy was taking about two minutes for every move. It turned out he had two Android phones taped to his legs, a couple of battery packs around his waist and a micro-speaker in his ear. A friend stationed over a hundred miles away was using Fritz to advise him of what moves to play.
What amazes me is the guy was so obvious. 1500's are capable of beating 2100's or occasionally a master, but not a GM and certainly not all in one tournament. Also, you can't choose to play an engine's top choice every time.
Of course, cheating in one form or another isn't new.
Confessions of a Crooked Chess Master – Part 1
Confessions of a Crooked Chess Master – Part 2
Cheating at Chess - Wikipedia article
Fischer: The Russian Cheated
Vladimir Potkin on coaching and cheating
I caught an opponent cheating me once in an OTB tournament. He was taking a long time over his move so I went for a walk. After a few minutes I noticed he had left the board and when I arrived back and sat down I noticed something odd about the position but it didn't quite register. After a couple of minutes staring at the position I realized what was wrong...he had made two moves! I think he played his move and while I was away, he decided to play something else and forgot to take back the first move. By the time I figured out what the problem was he returned to the board and I told him he made two moves. His reply was, “Oh! I made a mistake.” and he retracted one of them.
I can think of twice when I cheated. Once I cheated a preacher. It was in a postal game and he was pretty low rated. Just about every other move he sent (we were using postcards) was either ambiguous or impossible. In those days I didn't have a diagram stamper so had to sketch out the position by hand and mail it back with a polite note that his last move was impossible. This went on for many moves until I got tired of it. My solution was to send him a slightly altered diagram that set him up for a mate next move. He never knew the difference!
Another time in the first round of an OTB tournament I was playing a 1100 and expecting an easy win so didn't put much thought into my moves. After about 20 moves or so the TD walked by, looked at the position, chuckled and walked away. That's when I noticed the guy had a Q move that mated in one!! After several minutes thought he played the Q move and mated me, but he never said anything. I realized he was unaware that I was mated so I bashed out a Q move that offered to trade Q's. He thought for a couple of minutes, made the trade and I went on to win.
What can I say? Every saint was a sinner in his youth!