Thread: camera (webcam) software feature

i have seen that police cars have camera system (stalker dual) and there is one nice feature that i'd like to have in my system to.

feature is something like having video cache inside. like if policeman sees some accident he can push the save/record button and pc saves last 3 minutes of video (they can record situations what happened 3 minutes ago if they feel the need). i think, that there is small video cache inside, because camera isn't always in record mode. after pressing the save/record button, they see one videofile on harddisk, what they can trasfer to their servers.

does anyone know, is there that kind of functionality in some webcam software?