Video surveillance systems are used in all decent real casinos. The expression "heavenly eye" is especially common in American gambling, although also found in other countries.
The eye in the sky Eye in the Sky is the slang name for a casino video surveillance system.
Usually it is arranged in such a way that to hide from it in it's impossible. Often the coverage also covers adjacent to the building territories, offices, corridors and other areas. This explains such a nickname.
However, even the all – seeing employees of the service security, armed with the best cameras, can not always protect the institution from cheaters and other scammers.