A trio of questions about radio/smartphones
I know that smartphones can receive FM radio using earbud/built-in antennas, but can they receive amateur radio frequencies (144 MHZ?) and if so, how?
  


No. Any phones with built-in FM tuners will have the tuning limits determined by hardware.


  
  Is there a way to sending out radio waves and have them received as a call by smartphones?
  


Yes. Use a mobile network station. That's how they work. You will need a licence for this.


  
  Is there any other way of transmitting audio to smartphones in an area independent of cell towers/satellites etc?
  


Yes. Bluetooth and WiFi.