I want to make a product that involves sensing heat from a short distance (~ 2 feet). I don't need accuracy, just "hot or not." The sensor should be able to sit on top of a stove and tell me if an eye is on, or even more ideally I could have four sensors pointed at the four eyes/corners of the stove and be able to determine on/off for each eye (assuming four eyes on the stove).

What kind of sensor could do this for me?