The product you are talking about already exists, They use it in data centers and on commercial cooking equipment. Some use c02 and some use halon. However, good electrical practices and regular inspection would probably be a better option.
From memory I think the systems were Halon or co2 (long time ago) however the systems I have seen usually where activated by the fire alarm system and incorporated disconnection of electricity supply - no point putting it out if it will reignite..
Another point to note- the rooms had strobes to indicate activation ( in addition to audible ) primarily to prevent suffocation..
Yep, They dissipate all of the oxygen so nothing can burn. You don't want to be in a room when one goes off. Some are activated electrically(24v) and some use a big ass spring and a lead link.
I've seen the lead link system in boiler houses, they sit just above the burner in front of the boiler door. There also used for fire barriers in AC ducting.
For those interested it is basically to pieces of lead that overlap and is held together with solder that has a set melt temperature. Good for high heat fires not so good with smoke fires.
Anyone interested in rigging up a smoke detector to auto shut of the supply, I can provide some advice.