from the phone i want the files synced to the backup as soon as they are created. if i only sync those that i don't need then the once i do need never get synced.
unles you mean to sync first, then move files i want to keep on the backup only out of the way and rsync --remove-source-files those files again.
the problem with that is that when i do remove files on the phone, then it's because i need the space. at which point i don't want to wait.
syncthing does what i want. that is not the problem. them problem is only that it is easy to forget to set up ignore-delete, and that it's hard to monitor the sync status of the backup from the phone.
i appreciate the suggestions, but they don't really do much to help my case. what is really needed is an improvement of the syncthing UI and in particular a redesign of the way the status is handled.
for my backup maybe i'll set up an rsync with hard-links to create a second version of all files which protects them from accidental deletion.