If you want to play an Audio to the called person once the call was picked it, this is quite simple to accomplish with freeswitch / fusionpbx.
It’s not the most elegant way as I haven’t figured out yet how to add an extra confirm prompt for call groups in fusionpbx but for now this does the trick.
In the Dialplan, before transfering the call, add an execute_on_answer with nolocal
action export: nolocal:execute_on_answer=playback /var/lib/freeswitch/recordings/<DOMAIN>/<WAV FILE>
There is one issue with this, the audio starts playing much to fast, so add some blank audio at the beginning.