It's a long shot, but retrieving all electronic devices, especially cell phones and cameras, and trying to retrieve its memory, in the hopes of finding a recorded video from an incident/accident, would provide valuable information for the investigation.
Has it been done before? Or at least, are there legal implications that would hamper its use in the benefit of aviation safety?
There's an example of this floating around on YouTube: a video shot by a private pilot who attempted to turn around in a dead-end in the mountains and didn't make it. The video continues right up to the impact. The aircraft wasn't found for several years, and when it was, the videotape, which was strung all through the wreckage, wasn't immediately recognized for what it was. However, it was pieced together and restored well enough to show fair-quality images. The NTSB reference is DEN84FA308, and the accident occurred in 1984. The video is often shown to pilots for training purposes.
So, yes, if some videos can be recovered from the wreckage, they might be pretty useful, even if the cassettes are broken or whatever, and it has been done before.