Why not just purchase something like this
http://www.smarthome.com/7312/Drivew...MA-3000/p.aspx ?

Or this http://www.x10.com/products/sc546a_sp_tm_ps42.html

Or this http://www.gadgetshack.com/reporter.html

You get the idea. There are many other types of sensors you can use without
goiong through the hassle of reqiring the floodlights.