What is the thing that agent wear on their shoulder?
look this site for more details.. http://s1.postimage.org/n00csa6n3/Untitled.jpg
The thing worn on the shoulder by FBI agents and other law enforcement agencies is known as a shoulder holster. The shoulder holster carries two guns on both sides and you can check it out by visiting http://www.amazon.com/AirSplat-Shoulder-Holster/dp/B0006N07YU.
I would say a shoulder walkie talkie