A cellular telephone really is becoming quite a serious weapon. Cellular phones have been thought to be used to remotely activate bombs; in locations where cellular phone service is unreliable or nonexistant (such as the London Underground), it has been suspected the mobile phones activated bombs connected to the battery by turning themselves on via the 'Alarm' function.

In response to the July 2005 London terrorist bombings, the New York subway has investigated blocking cellphone signals.

It basically comes down to the fact that cellphones happen to make quite a good detonator button, one that can be pressed from pretty much anywhere by anyone who knows the number. A cellphone could be used to dial a special extension on a computerized PBX that begins destroying evidence on a hard drive, etcetera -- then remove the extension from the PBX's database.

It's just another way of pushing the button.