Noun
hailer (plural hailers)
A person who or a device which calls, summons loudly, or hails.
So go into your local branch of UBS, and say "I'd like to open an account please.", and when they say "What with?" take out a loud hailer and say "NAZI GOLD! Just like you did! Bill Bailey
Additionally a "Loud Hailer" was installed opposite the crew entrance door for communicating with downed aviators on the ground or in the water. Source: Internet