According to a FTC report, emergency PIN systems won't help make ATM users any safer against criminals. This Washington Post article reviews the FTC report and the concept of these systems:
An emergency PIN would allow a customer in trouble to enter some variation of the regular PIN to summon police. [...] The reverse PIN has been rumored for years to be installed on ATMs, but this is an urban legend.
Ken Tumin5,442 posts since Nov 29, 2009 Rep Points: 123,743