Sorry for the delay. In checking this through, I discovered I wasn’t running of a linked version of service-runner but rather one I had copied across when you were developing this.
Backup is too cute for that, it checks for service-runner running (a good thing normally) 
@TrystanLea, see below still not sure what is preventing this working. Something is failing silently.
[edit] @Greebo, trying to think of ways to debug this:
Is there a way to monitor redis? I found a log but there is nothing in it.- Is there any way to sent a test message to redis for service-runner from the command line?
Backup is definitely getting to the point of sending the key to redis.
So I have discovered redis-cli --slave The command is definitely getting to redis…
"RPUSH","emoncms:service-runner","/var/www2/backup/emoncms-export.sh /tmp/emoncms-flag-export>/var/www2/data/emoncms-export.log"
Should I see that service-runner pulls the token off? If I try an lpop there is nothing there.
Does service runner do any checks on the command given or the return value?
I am wondering if it is file permissions again.
Could service-runner emit a heartbeat to the syslog?