Disruption of communications can be an important and useful tool for military and law enforcement applications.  By limiting the availability of cell phone signals, law enforcement representatives are able to effectively gain control the communication in an area  This can be particularly useful in several scenarios, such as:

1>    Prisons: The use of cell phones in prisons has been linked to witness harassment and targeting, smuggling of illegal items into prisons, and escape plans.  By effectively shutting down cell phone service within the prison walls, officials gain control of the inmate population’s communications by forcing them to use monitored phone lines, effectively stopping any nefarious planning in its early stages.

2>    Police Raids: Police and SWAT teams serving high risk warrants or searches often use a cell phone jammer in the area prior to the raid.  This disrupts the ability of the suspect to warn others, communicate, or otherwise make strategic plans which could impede the law enforcement officers' objectives.

3>    Military: Military uses of a bomb jammer include scenarios related to those above, as well Use of cell phone jammer for militaryas deploying the jammers in forward vehicles for convoys or escorts.  By blocking cell phone signals in an area, cell phone remote detonated IED's are effectively rendered useless.  Many special forces units are now employing smaller man-pack jammers for patrols, to keep them safer as well.

The civilian market has also taken to use of smaller, less powerful cell phone jammers, which are now used in schools to prevent cheating on examinations, as well as other areas such as funeral homes, theaters, and places of worship, where cell phone disruptions are improper and obtrusive.(from thejammerworld.net)