Originally Posted by snopercod
I have one of those. It's a $13 digital meat thermometer with the probe stuck through the firewall. It doesn't have an alarm so would only serve as confirmation of a fire. I also installed a 3/8" aluminum tube "spray bar" in front of the firewall which is plumbed to a fitting on the panel into which my Halon fire extinguisher nozzle fits. I hope I never have to use those things.
IIRC, there have been tests showing that halon in a piston engine cowl can't compete with the hurricane of cooling air, and just blows out the exit. I'd be more prone to save the halon for me. :-)