With the sometimes questionable construction of mining rigs and running lots of GPUs with lots of power in tight spaces, I wonder if having a fire alarm directly over the setup would be a good idea.

What smoke/fire alarms would be good for electrical fires?  I have this nagging suspicion that the $5 ones at wal-mart aren't the best. 
 
Maybe even have it rigged so if there's smoke the power is automatically cut...