Surveillance cameras alone were not enough to locate the Boston Marathon terrorists. Israeli hi-tech company BriefCam enabled investigators to summarize an hour of surveillance video footage into only one minute and also zoom in on people and objects whose movements changed during the filming. The system then tracked those movements from the beginning of the video.
http://www.jewishpress.com/news/israel-hi-tech-firm-helped-capture-boston-bomber-terrorists/2013/04/29/