I use MobileOrg with webdav, both remote over ssh/tramp, and locally
(two separate setups).

On the ssh one:

(setq org-mobile-directory "/ssh:foo.example.org:/usr/home/gdt/ORG")
(setq org-mobile-inbox-for-pull
      (concat org-directory "/from-mobile.org"))
(setq org-mobile-use-encryption t)
(setq org-mobile-encryption-password "password")

But, the tricky part is dealing with permissions.

Basically, the webdav world seems to want you to only access it via
webdav, and joint filesystem and webdav access is troublesome.

My remote directory is (on NetBSD, which I think inherits gid even
without the SysV-style sgid directory):

drwxrws---  2 gdt  www  512 Mar  2 09:08 ORG/

and I run this script from cron every 5 minutes:

#!/bin/sh
cd /home/gdt/ORG

find . -type f \! -group www | while read f; do
    echo -n "GROUP "; ls -l $f
    chgrp www $f
done
find . -type f -name mobileorg\* \! -perm -220 | while read f; do
    echo -n "MODE "; ls -l $f
    chmod g+w $f
done



An alternative would be to have a webdav fs on the machine with the org
files, and to use that to write to the webdav area.

My webdav setup is straightforward apache.