@thcrozier - accelerometers
Nothing wrong with your idea from my point of view.
I ran a project at the end of the 1990s trying to use the cheapest INS we could build (and compare it with some aerospace solutions). One of a number of options we tested used the components from the earliest wireless computer mouses. One thing you need to know is if the data runs over any kind of persistent memory. It has long been common 'state of the art technology' practice to use multiple 'inaccurate sources' and run the data through processors which create 'accurate output'.
As i said before, if you dont get it from (the QAR and maintenance computers, you go to) the FDR/CVR, then on to possible other memory, and finally to the more out of the box and innovative solutions.