I can see the need for a warning - but why go to the bother of wiring it into the computer. Overheating doesn't happen suddenly, it builds up over time, so I would have though a light or a bell on your housing would be sufficient.
If you already have an external E stop switch, then by all means, add a relay in the circuit to close this if you are over heating, but otherwise a warning of some sort, will enable you to hit the E stop on the computer to shut down. You will also know why it has shut down as well.