This is an excellent idea! I was mugged on the doorstep of my apartment building a few months ago, and even though I moved into a much better part of town, I'm still really paranoid... and my circa 1940's house doesn't have much lighting in the back yard... I think with some simple circutry you could even turn this into a more permanant thing; with a new house payment I can't exactly afford an electrician right now.

Thanks for the great idea!