The NYPD is looking to create a mobile version of the kind of full body scans we're all used to at airports, in that it'd show the shape of objects stored underneath clothing. The system would allow police officers to spot armed passerby on the street without ever having to get out of a police van.
The scanner, announced Tuesday morning by NYPD commissioner Ray Kelly, doesn't quite sound like it's ready for prime time just yet. Right now the device, produced in concert with the Department of Defense, only has a range of three to four feet. The commissioner is confident that this range can be increased to upwards of 80 feet, which would be more than enough to reach a sidewalk.
The actual particulars of the system are pretty ambiguous (infrared is the prevailing guess, though everyone appears to be pulling from an unsourced mention of IR at the end of this NY Post article), as well as when it's actually expected to hit the streets, though apparently it's been in production for at least three years.