Ok so this thing is literally just a phone to USB audio adapter so it's utterly distressingly easy to grab the audio, so now I just need to figure out Asterisk, I'm sure this will be easy
(Matthew died on his way to understanding Asterisk)
@mjg59 I found Asterisk too complex and had more success with FreeSWITCH. It has a nice default configuration with some extensions and an echo extension.
Nowadays I've switched to Flexisip- I don't know if it was easier because I had already figured much making FreeSWITCH work.
(I've switched to Flexisip because in theory it can do push to mobile devices.)