A secure entry system makes use of radio transmissions to communicate with locks, keys, and related components throughout the system. The radio transmissions can be made using a paging system, a cellular telephone system, or any other RF carrier. Some embodiments employ a cellular telephone in lieu of an electronic key. Others integrate a paging receiver within an electronic key to provide a unit with dual functionality. The system is illustrated with reference to exemplary applications in the industrial site security, real estate lockbox, and transportation fields.