One phone-sized device can block cell phone signals in a 20 foot radius.

CNN: Mobiles used in high-tech terror

Representative Henry Waxman (D-Calif.) is tapping Wu for advice on legislation that would make it illegal for phone companies to block access to the Internet on mobile devices.

FORBES: Magazine Article

Allow prison governors to block mobile phone signals, to prevent inmates from carrying out illegal activities while inside.

BBC: Bill-by-bill: Guide to MPs' private members' bills