Been keeping track of this project on Github, but going to give it a go here.
So far progress is swift, the basic hardware has been selected and playback is working well. A workable hook design is in place and I'm hoping to spend some time on the management UI next.
If you want to get away from a physical switch, consider a magnet switch. They are encased pretty well and make for harsh environments. You'd have to add a magnet to the handset of course, but... magnets!