Chicago aldermen endorsed a measure that would require those who make money off unlocking the devices to keep records on their customers.

"The idea is similar to a city law requiring pawn shops to track who walks through the door and sells them merchandise. It’s mostly small cell phone stores that unlock cell phones and tablets, which is the process of severing service from the original provider so a new owner can use it. Such stores would have to get identification from the person paying to unlock it, along with identifying numbers from the device. That information would have to be reported daily to Chicago police," said the Chicago Tribune.

Anyone caught unlocking the phone without taking those steps could be charged a fine of up to $1,000 per unlocked phone, the Tribune said.

Last year, 12,730 phones were reported lost or stolen in the city, the Tribune said. About 80 percent of stolen and lost phones headed to the black market are unlocked at small cell phone stores, and the rest are unlocked by individuals with some computer skills and the right program. Once a phone is unlocked, it can fetch up to $200 on the black market, said Sgt. Edward Wodnicki, adding that cell phone thieves have told him they “can make more money selling phones than (they) can selling dope on the street corner.”

Chicago aldermen also have proposed requiring all cell phones sold in Chicago to have a so-called kill switch, or a way to render them useless once they are lost or stolen.