Self-cleaning bathrooms is a good start, because bathrooms are typically dirty. Why stop there though? As we go farther, the problem gets substantially more com

Self-cleaning bathrooms is a good start, because bathrooms are typically dirty. Why stop there though? As we go farther, the problem gets substantially more complex, but imagine a system where cleaning bots were small enough to travel through your walls. They clean while you sleep, so as not to inconvenience you. One possible problem would be transporting the cleaning materials. I think small in-wall robots would be very effective, but they wouldn't be large enough to carry a lot of cleaning fluids. Having to travel back and forth to a central hub to reload could be costly as far as time is concerned, but poses an interesting path-finding problem.