The Kenmore microwave we got in 1988 has this very feature, but it requires a probe that's pushed into the food and plugged into the side. Long ago lost.

But I did use it a few times and liked it. Just too much trouble.

If you want sensors to see the inside temp of something, that may be more expensive than the microwave. Surface temp is unlikely to be good enough, but it is easily measured with IR.

wow that was weird, i had a dream that i read this article like two days ago and know what would work, it would have a hard drive that remembers the food you cook and what temp it is that way you would only need to cook the food once and the microwave would know what food and time it takes.

I think they should at least include a smoke detector in all microwaves that will automatically shut off the power if it starts to get too smoky. This would prevent a lot of fires or totally ruined meals.

You can get one of those hand held non-contact thermometers pretty reasonable. The sensor might cost $10 or so, and the electronics would be pretty easy to interface with the typical computer in a modern microwave oven.