Some cell phone models now offer two-way communication capabilities, much like traditional "Walkie-talkies" that service personnel sometimes use, although linking distance is only limited by range of the telephone network.
A walkie-talkie or two-way radio is a hand-held portable, bi-directional radio transceiver. The first walkie-talkies were developed for military use. Major characteristics include a half-duplex channel (only one radio transmits at a time, though any number can listen) and a push-to-talk switch that starts transmission.