This DIY Fire Alarm Clock may be overkill, but hey, maybe you’re a little deaf? Eh? What’s that you say?
This hack takes a standard cheap alarm clock, some interface components and a fire alarm bell to get the job done right. Normally these small alarm clocks use a piezo buzzer to attempt to wake you up. The alarm signal is hijacked from the clock circuit board and used as an input to the interface board.
Great idea, for a PRANK to your roomate even.
I’ve seen this done in the past with other clocks, including an Atomic Clock
http://www.atomicclocks.com for some examples