In reply to LastBoyScout:
Does your mum read SunTzu?
'In his retreat, Sun Pin came to a narrow defile, which he calculated that his pursuers would reach after dark. Here he had a tree stripped of its bark, and inscribed upon it the words: "Under this tree shall P`ang Chuan die." Then, as night began to fall, he placed a strong body of archers in ambush near by, with orders to shoot directly they saw a light. Later on, P`ang Chuan arrived at the spot, and noticing the tree, struck a light in order to read what was written on it. His body was immediately riddled by a volley of arrows, and his whole army thrown into confusion.'
One of those motion sensing flood lights might do it. You can run them from a normal 13 socket, so could set one up quite quickly. You can also get wifi enabled security cameras. Not sure where you'd get the archers from though...