Since it takes about three minutes for a microwave to heat up a meal that has been prepared and stored in the refrigerator, I would prefer to have my food refrigerated until just before I eat it, just to be on the safe side. Three minutes is a neglible amount of time to wait for the meal to become hot.

Well sand what do you think about the same concept but for an oven?

The problem is not with the heating apparatus (an oven takes longer to heat up and uses more electricity) but with the storage of the meal before heating. Outside of a refrigerator food is tempting, not only for humans, but also for bacteria that are always looking for stuff to munch. A refrigerator discourages this, but leaving a meal uncooked in an oven or a microwave for several hours makes a nice bacteria picnic which is likely to be poisonous to people.

Actually you could store your food in the oven, program it to come on at a certain time and cook the food without worry of food poisoning. The heat from the oven would be sufficent to kill any bacteria present. This is assuming you cooked it long and hot enough. The end user of this invention would have to sacrifice things like taste, preparation and variety for the convenience. I think most of us would be better served by using a crock pot- veggie, meat and gravy all in one pot waiting when you come home.

Whether or not food kept at room temperature depends upon the food. Food prepared with raw eggs is especially prone to produce ptomaine poisoning and once the toxic products from bacteria are produced the bacteria may succumb to heating but the poisons remain.

Notwithstanding food safetry, some microwave ovens have timers, I know ours does.