Subject: HELP: Do electronic programable random beepers exist?

For a classroom experiment, I am looking for an electronic device/kit that can be 
programed to beep at continuous random intervals within a set time parameter. The 
specifications of this device/kit should include:

- a moderate decible beep (loud enough to be heard over talking students in a 
classroom)
- adjustable programing to change time parameters easily up to 30 mins thereby 
changing the mode of beeps (i.e., day 1- random continuous beeps between 0 to 5 
mins, mode=2.5 mins, day 2- 2 to 8 mins, mode= 5 mins, etc.)

Does this exist in a kit form or does this device exist?  I've scoured the web 
and found only one similar item (using an ear plug instead of a speaker for beep 
for $300!).  Any info would be greatly appreciated.  Thanks
Mark

Re: HELP: Do electronic programable random beepers exist?