Just saw this tool featured in Wired: they call it a laser pyrometer.
But the company that makes it, Black & Decker, refers to it as a thermal leak detector.
What does it do? It shows you where air is coming into or escaping from your home. Basically, it does the same thing as an expensive home energy audit. But this little tool only costs $50.
Your home energy savings, however, could more than make up for the cost of the tool very quickly...