While impressive, after watching his videos it becomes apparent it's a vulnerability in that one particular model of lock. Not quite as impressive.
I wondered if other passive methods (radiography) would be applicable but they all seem to rely upon having a sensor behind the subject. I suppose your suggestion would be something like sonar, however I cannot find any clear references to the difficulties of the applications of such techniques through solids. Did find this interesting tidbit, though: http://en.wikipedia.org/wiki/Anti-frogman_techniques#Ultraso...
You might like, http://www.washington.edu/news/2013/06/04/wi-fi-signals-enab...
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