Multiple FDR?
In general, an aircraft carries a single FDR, built and armoured to withstand very high deceleartions and intense fires. It is also located within the airframe in a position where it is likely to remain in the main debris field following any impact.
With modern technology would it not be possible to install several light-weight FDRs, not so heavily armoured or fire-resistant, in structural elements such as the fin or wingtips that are likely to break off in a catastrophic impact, and end up in the outer fringes of the debris field, or even float in the case of a break-up on impact with water.
It should be possible to construct such a recorder with a form factor similar to a mobile phone and with similar power requirements. It could even be fitted with an RFID tag to aid in location.
I'm not suggesting that these mini-FDRs (and CVRs) should replace the current concept, but a lightweight recorder at the top of the fin could have told us much more than we might ever know now about the final minutes of AF447.