Terrorists used a 'body bomb' in an attack on a Saudi Prince. The explosive was implanted in the terrorist's body and set of by a cell phone. It is unclear exactly what if any screening the man went through, but such devises seem exceptionally hard to detect. This could become a massive security problem.
Video embedded below. (from http://hotair.com/archives/2009/09/27/video-the-implications-of-the-body-bomb)