I haven’t done this, but it’s a long term goal. I want to get an infrared laser diode temperature sensor module and design a dust shoe to integrate it so that the sensor is just behind a 1/16" thick clear blast shield of polycarbonate, pointed directly at the router’s bit. The module communicates over i2c, so it needs a microcontroller to manage it. I’d probably go with an ATTiny2313. Program it to have all kinds of alarm outputs: Temperature increasing too quickly, temperature too hot, temperature changed instantly (bit broken), temperature isn’t warm enough (bit broken). Mount the tiny controls board on the gantry and just run power and alarm wires back to a controls arduino that can trigger a pause job or e stop command.