That's literally how the sensor cooking functions on microwaves work, unless it's so cheap they're just preset times. Usually this works through a steam sensor, popcorn sometimes uses a microphone, and the obvious place this is going is to just point an IR camera at the food to see when it gets hot and even automatically pause for hot and cold spots to even out. I've not actually seen this in a microwave, but that's just because new microwaves don't have the big transformers worth taking them apart for.