There are many variations of this - and you can easily make your own by washing out a spray bottle, filling with water, and adding a couple of drops of lavender/eucalyptus oil. A few squirts in the corner will get rid of any "nasties" and also leave the room smelling fragrant, without chemicals. This one also sports a glow-in-the-dark label, so it can be seen easily in the dark by a child. Yet another little tool to help parents without having to leave the lights on at night.
You can get this anti-monster spray from http://www.theinthing.com/.
*Isn't this Halloween material fantastic? I've no idea what I'm going to do with it, but it's just beautiful.