If you should ever be forced by a robber to withdraw money from an ATM, you can notify the police by entering your PIN in reverse. For example if your PIN is 1234 then you would put in 4321. The ATM recognizes that your PIN is backwards from the ATM card you placed in the machine. The machine will still give you the money you requested, but unknown to the robber, it will call the police and they will be immediately dispatched to help you.
Hoax or Fact:
Mixture of hoax and facts.
The claims in the message are not true. It is a fact that such a software to detect Reverse PIN technology for ATM does exist, but it not implemented by all the banks universally. If banks are to install such safety systems they would definitely provide necessary information to their customers explaining the safety system, and how to use it.
Therefore, at this point of time, if you are entering your ATM PIN in reverse order, you are only likely to get an error message saying "incorrect PIN", and the probability that it will call police and they will be alerted is zero. Such a security system is not in use because of certain practical reasons. More over, the banks oppose to maintain such a system. For further details, read the reference section.