Many modern handhelds (like the BTECH GMRS-PRO Go to product viewer dialog for this item.
sending short text messages over analog audio using handheld radios transistor radio
Apps like Rattlegram or Ribbit allow you to send text by holding your phone near a standard radio's microphone. The app converts text into a series of audio "beeps" (digital noise) that another radio can receive and decode back into text. Many modern handhelds (like the BTECH GMRS-PRO Go