The New York City Police want to help you find your lost or stolen iPhone, which is nice! That's why the NYPD will implement something called Operation ID, beginning Friday, September 21st--not coincidentally the date the iPhone 5 goes on sale. The police will be on point for that, too:
"On Friday, officers will be stationed at 21 stores throughout the city, including six Apple, as well as seven Verizon and eight AT&T stores as part of Operation ID.
"The program is free to the public. Officers will register the serial number of the electronic device along with the owner's name and contact information. Items can also be engraved with a unique serial number."
The police will be glad to assist with registering any electronic device, not just the iPhone--you can do this at any precinct through a crime prevention officer. They also recommend iPhone owners use "Find My iPhone" as well.
Operation ID has been in place in one form for a while, but Police Commissioner Raymond Kelly said in a statement quoted by the Associated Press that "theft of Apple phones and other hand-held devices drove the spike in robberies and larceny" in 2012, hence the new effort to raise awareness among smartphone owners.