adafruit/Adafruit_FONA_Library — pull request #19 by samyk (2014-12-08 09:51:15+00:00)
Title: Added getSMSInterrupt/setSMSInterrupt functions to allow RI pin to interrupt upon inbound SMS

You can now use setSMSInterrupt() to enable/disable the RI pin to send an interrupt upon receiving an SMS. Previously, FONA would only interrupt upon receiving calls so you would need to poll for new SMS', now you can simply listen for the interrupt and tuck your microcontroller in and put it to sleep.