Automated? Maybe not.
I think if you listen to the video sound track (link was a couple of posts back) it's clear that this is not an automated announcement - indeed the pitch and intensity appears to rise as the touchdown proceeds.
Is there any evidence that the "brace position" actually saves injuries anyway? Many passengers might think it's a better bet to fully-aware of what's going on around them and adapt their strategies accordingly rather than be cowed into an ostrich-like heads-down stance.
But I was just interested to know whether this constant repetition was something taught at Delta's flight attendants' training.