Mechatrommer is just making a general point. Nitpicking his post is stupid.
I just have to love it when the pilot police show up to demonstrate their knowledge of stupid-shit-no-one-cares-about. (When it's not germane to the point).
Of course an accelerometer would be useful if the pitot tubes went out. At least it could tell the pilot an continuing approximation of his air speed based on the last valid readings. And it could be fairly accurate for at least some duration. This would be highly useful if the pilot hadn't happened to be watching his airspeed at the time of sensor malfunction. Maybe it could also display a second figure, increasing over time/conditions, to let the pilot know how much salt to take with that reading.
GPS plus elevation and pitch could also be used for some ballpark figure, at least.
It seems bizarre that a failed pitot tube can result in AF447. The pilots can't even tell they're in a stall. And even after the sensor thaws and works perfectly fine, again, more than a minute before they could have saved the plane, they just didn't trust it.
With some backup that said: "yes.... your super low airspeed reading sounds right to me, too" that could have changed the outcome.
Human beings are apparently completely incapable of estimating airspeed devoid of visual reference. Any sort of backup might be useful.