So, I would like to connect a GSM module to my Pi to act as a phone, and be able to make a two-way call to my cellular phone. I know this is possible, and have seen a few tutorials on this (https://www.raspberrypi.org/blog/piphone-home-made-raspberry-pi-smartphone/).
However, I am wondering if it is possible to have the Pi listen for keystrokes from my cellular phone during the two-way call. Ex) The Pi calls me on my cell phone, I pick up and a two way conversation is going, and when I press a number on my keypad, the Pi receives info of which number I pressed.
Is this possible and how would one go about doing it? Would I need to use something like asterisk?