We have found that often we put something in the microwave, start it, walk away, and get distracted only to find rotting food in the microwave the next day. One problem is that the light in the microwave is only on during the heating of the food, and goes off - so the food is invisible and easily forgotten.
I propose that a simple but accurate weight mechanism will keep the light on the interior of the microwave anytime food is left in the unit. This weight mechanism would then also be able to provide time estimates for heating and cooking based on the weight of the material being heated. An option to weight the empty dish and to have a database of empty dishes in the memory of the microwave would also be made available.
We estimate that in given year we throw out more $30 dollars of food accidentally left in the microwave, happens at least twice per year. Multiple that by millions of households around the world and millions of dollars of food is lost per year.