Rick W...
As a teenager, I had an uncle who liked to play practical jokes. Upon visiting a fireworks factory I found the perfect "get-even". I can't remember what it was called, but it had two wires, one to attach to power and the other to ground. It would set off a loud whistle, produce prodigious smoke and end with a loud bang. Attached to the low voltage side of the ignition coil of my uncle's brand new car, it more than got even for all his indescretions!I don't know how a glow plug could be used to set off a a flare's scratch cap, but it worked wonders on any match-lit fuse!