There is a project here:
https://www.mobileread.com/forums/sho...d.php?t=174066
that stalled over problems with the Kindle alsa implementation.
Until they hit that snag - they were making good progress in getting VoIP working on the Kindle.
Myself - I don't need a book that will make a telephone call.
But since that mountain was there, the members of that thread where climbing it.