The solution I like the best is to have a buzzer sitting close to the hawk that is triggered by a remote you can have in your hand, but I dont know of any examples of where to buy a gadget like that off hand.
Try a wireless battery powered doorbell.
Well, arent I a dumb ass....
Geoff Hirschi - "It is better to have lightning in the fist than thunder in the mouth" Custom made Tail Saver Perches - http://www.myrthwood.com/TieEmHigh/