I've seen reports of mobile phone jammers being used in Iraq to prevent the triggering of  IED's, it may be that the police will deploy these around protests for 'Public Safety'. As a backup there are many cities now with wireless open-air networks. Setting up a wireless network is reasonably easy, however you would need a point to connect it into the rest of the worldwide network, that would be the more complex part.

Any idiot can face a crisis - it's day to day living that wears you out.