Such measures are applied in industrial installations (like in electricity
cabinets of large machines in a factory - where water sprinklers are not a
wise anti-flame option). In non electrical / non chemical environements
water sprinklers remotely and automaticly switched open (for EE guys, open
means there's a current of water) by a relay connected to the fire / heat
alarm. Im sure there are trip-switches that also disconnect elevators and
such when there's a building fire...
Seen a LOT of panels/Other for the Nuclear & PetroChem industry's (cant say
I ever seen any automated fire ext kit for a sole peice of electronics)..
In reality, If something is allowed to get hot enough to burn your house
through an electrical fault (dead short) then it means that the consumer
unit is not properly set up. Once a fire is started removing electricity
(for most things that we have) will not stop the fire. Normally IF there is
a fire you would combat the whole area and not just the specific fire point
of detection (speaking about automated fire systems here).
But I would need to wonder HOW his pc burning (probably have 5-10 fuses
before it gets to the power strip) will spread to other things in the house.
Metal (normally metal) cases generally dont burn well, nor does the things
inside of a case.
My suggestion, Get proper electrical wiring.