One problem my roommates and I have is figuring out whether the dishes are dirty or clean. How could you design a dishwasher to always tell whether the dishes inside are clean or dirty? How can we work around the current dishwasher design to figure out whether the dishes are clean or dirty?
Weigh the dishes. A dishwasher that had a built-in scale could tell when something had been added rather than taking out. If the weight increases while the door is open, then the contents are dirty. If the weight has only decreased so far, then everything is still clean. This would fail on edge cases like taking out a clean dish and putting in a dirty one at the same time, but most people don't pretend to be Indiana Jones while managing their dishes.