Surveilluminescent lights on a stick, make long-exposure light trails like a waving flag in front of a surveillance camera, revealing its otherwise hidden field-of-view.
<a href="//commons.wikimedia.org/w/index.php?title=User:Glogger&amp;action=edit&amp;redlink=1" class="new" title="User:Glogger (page does not exist)">Glogger</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>