Quoting their web site:
What is "Nude It" and how does it work?
Just like the vacuum cleaner or the cell phone, "Nude It" is a byproduct of the space program, and so far we have seen this technology used only in airport scanners. However, a German developer team has managed to apply this technology to something very small and practical that everyone is able to use on a daily basis: the iPhone. "Nude It" is also the first app in history that can be purchased, downloaded, and installed outside of the iTunes store