From my own research I do not think that currently there are people who can see other players cards but by googling a lot of stuff the closest thing i have found are RNG cracking programs which figure out the algorithm of the RNG based upon previous information and can then tell the current cards once the RNG is cracked. There was a program called Blackjack
Killer which showed the dealers hole card and the next card that was coming but the website has since been removed and the program is not available on the internet. A couple names of the programs I have found that have touted the ability to see opponent cards are Diabolic and PokerRNG. The youtube videos show how the program can decipher flop cards as well 1 opponents potential hole cards. The diabolic program looks like it links to Pokerstars RNG and tells
all the hands. Having said that, I have never had one of the programs so I have no idea if they actually work. Secondly, like what happened with Absolute Poker and potripper, there are a lot of math people that play poker and when an opponent calls all-in with garbage or huge bets on the turn to hit miracles and never loses hands it gets people to take action and look at the stats so people get busted. Secondly, poker rooms scan for background programs and probably bust people who use those kind of programs. So its all very unlikely that someone can see your cards. Finally, i figure it is technically possible for some genius programmer hacker to develop a program that sees all the cards and is doing it somewhere right now.
Here is one of the videos for poker:
Here is one i just found for craps:
I can no longer find the blackjack video for blackjack killer. I think the guy got busted or something and deleted it from youtube. I have no idea how legitimate these programs or videos actually are but since someone asked if it was technically possible, with these programs, I had to at least think so.