I've written a script that every minute tests to see if the appropriate rsync command is running. If not, it simply runs it again. In that way it effectively restarts and gracefully resumes.

This Google search:

https://www.google.co.uk/search?q=rsync+auto-restart+failed+...

returns this link:

http://superuser.com/questions/302842/resume-rsync-over-ssh-...

which contains this script:

    #!/bin/bash

    while [ 1 ]
    do
        rsync -avz --partial source dest
        if [ "$?" = "0" ] ; then
            echo "rsync completed normally"
            exit
        else
            echo "Rsync failure. Backing off and retrying..."
            sleep 180
        fi
    done

The comment says:

    When the connection dies, rsync will quit
    with a non-zero exit code. This script simply
    keeps re-running rsync, letting it continue
    until the synchronisation completes normally.

That's pretty much what I've done.

Yes, it it does, if you use:

   --partial               keep partially transferred files

   --append                append data onto shorter files

You mean, if the connection fails before completing? I don't think so (I believe that's a feature).

For automated transfers ("retry until done"), I use the lsyncd wrapper (which also watches the source files, so you don't need to poll for changes: it wakes up by inotify).

Sure, just use --partial switch:

   --partial               keep partially transferred files