Transit coaches are equipped with fire detection systems. Gillig likes to use a system where you string a heat sensitive wire through the engine compartment. In the event of a fire or a broken exhaust, the two conductors in the wire would internally touch and set off the alarm. Nova RTS coaches often had specific sensors which would simply close their contact in a high temperature situation. It would open again after cooling down. They are about the size of a AA battery. The fire wire requires replacement after excessive heat exposure. Both cases would be easy to connect to Skyview of even a simple panel light.
A very small 12V compressor, a pressure switch at the other end joined by a length of nylon tubing, like the Vans brake line/safe air pitot tubing or similar. Should a fire impinge on the tube, it will be breached, the pressure will drop, and SkyView can then read the difference in the switch state.
You should be able to cobble something together for less than $50.