I've watched all the episodes of Aviation Disasters. The device missing from cockpits is the video recorder. Many investigations revolve around questions like what is the pilot looking at, what the instruments show, even who the heck is in the pilot's seat. Video can confirm switch settings and instrument readouts (the voice recorder is also used to confirm if the warning horns sounded properly). Instead, a lot of ef…
Also video occupies much more data than most other streams of information stored on blackbox. This coupled with the fact that anything aviation related takes decades to get into widespread use and it was only quite recently that solid state storage became so dense and ubiquitous.
Video surveillance at airports is getting more widespread, just search for SFO asiana.