I've used a wired mouse and keyboard over USB and it worked fine. But I don't have a BT equivalent so I don't know how well they work.
I'm also not an emacs user, so I can't comment on how good this port is. However, I've used my phones with terminal emulators and setup busybox and ssh and vim work fine.
For quite a while I even used a spare android phone as a remote log monitor when we were developing something and a tricky intermittent bug would show up. I just brought it around with me to meetings, wherever and just tailed a log file to keep an eye on things. It just sat under my normal monitor most of the time acting like an extra mini-screen.
