Can you elaborate how there is no need for hardware changes?
Are you connecting through the earpiece somehow?
Some time ago I hacked our flat intercom. I needed to have a text message delivered when the intercom rang (we use it to open door to the building), I had to tap to it with an arduino.
Some time ago I hacked our flat intercom. I needed to have a text message delivered when the intercom rang (we use it to open door to the building), I had to tap to it with an arduino.