This is interesting, “Blastwavelabs” bought a portable cell phone jammer from a company called DealExtreme, it appears the jammer ships set to frequencies outside North America but it can be modded to work by turning the trim pots a bit (small potentiometers to tune/trim the voltage)… I’m not sure that would actually work that great without a spectrum analyzer, either way a fun read and please debate in comments about a device like this… – Link.

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Personal cell phone signal blocker device ($48 – not sure what’s up with this company, proceed with caution) – Link.

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Wavebubble open source RF jammer – Link.