This is a "Skimmer" Attached to an ATM

This skimmer was found last year, attached to the front of a Citibank automatic teller machine in California.

This is fairly professional job: Notice how the bulk of the electronics fit into the flap below the card acceptance slot. Also, check out the tiny pinhole camera [on the left, underneath the slot], ostensibly designed to switch on and record the victim’s movements as he or she enters their PIN at the ATM.

Neatorama has previously featured "traps" that physically steal the ATM card, and totally fake ATM machines. To counteract these skimmers, some ATMs "now oscillate the card back and forth as it is motored into the machine, effectively not providing a smooth "swipe" these skimmers need." Other ATMs incorporate GreenSleeves, but criminals have devised fake GreenSleeves!

http://www.krebsonsecurity.com/2010/01/would-you-have-spotted-the-fraud/, via Reddit.

Wow, that's remarkable... And the fact that they're DIY, made out of scavenged MP3 players and so on is even more amazing. You'd think that someone with the sort of skills required to do this could get a real, high-paying job instead. They have an admirable skill set!