U.S. cellphone carriers were offered a technology last year that supporters say would dramatically cut incidents of smartphone theft, but the carriers turned it down, according to sources with knowledge of the proposal. The so-called "kill-switch" software allows consumers to remotely wipe and render their phones useless if stolen. Law enforcement and politicians believe the incentive for stealing a smartphone or tablet would be greatly reduced if the technology became standard, because the devices could quickly be rendered useless.