Would mechanical indicators have helped in the Air France 447 incident?
Unfortunately, if there had been a jazz band in the cockpit singing "The plane is stalling" it wouldn't have helped. If Moses had been in there carrying a stone tablet newly-carved by God himself inscribed "Pitch down" with a host of angels to help announce it, that would have made no difference.

The unrecoverable problems were in the pilots' brains and in the communication between them, not in the aircraft or the technology.

Once in that state, only a fresh perspective (for example stepping back from the problem, bringing in a fresh person to look at it, using a checklist) is likely to snap those trapped in it out of their spiral: of alarming events, inappropriate reaction, unexpected result of the new inputs, and mounting panic.

It's a common experience in many crafts and disciplines, though in some - like computer programming - it's easier to find the new perspective than in others, such as piloting or surgery.

Anyone who has found themselves in that spiral will be able to tell you that adding more data or new sources of data to the mix rarely help.

It seems reasonable to think that a clear, simple and apparently unarguable piece of evidence would be the way out of such a situation. Unfortunately, in practice, it rarely if ever is, and there is nothing to suggest that in this case it would have been any different - despite compelling intuitions to the contrary.