Well, we already have single purpose household robots such as the Roomba for floors and the Mowbot for lawns, but neither one has any appreciable AI capability. Perhaps that can be improved upon. Extrapolating, primarily to benefit the handicapped, automated cooking and other aspects of meal preparation would be nice. It's a horrendously formidable task, but the payoff would be worth it. I suspect that if such is developed, it would be integrated into a full "smart house" system, but there's no reason not to work on subsystems independently.
Artificial pets are becoming more sophisticated every day, but there's still a long way to go toward realism. That might sound frivolous, but it isn't. When we put my mother in a care facility, I reclaimed my Lucy the cat from her. That was disheartening, so I bought her a robot replacement that looked almost exactly like Lucy. The brand name was something like "Fur-Real", and it was quite adorable. Subsequent generations have become even more life-like, but they're still not quite there. My mother clung to that thing almost every waking moment, so much so that the facility staff bought her a replacement a year later because the servos had worn out. That one expired in about a year as well, so they gave her a third one which outlived her. For someone who is lonely or just loves pets but can't have a real one due to allergies or an inability to care for one, an artificial replacement can be very gratifying. Perhaps you could improve upon the status quo in that field.
I have other stuff to do right now, but I'll think on it some more and let you know if I come up with anything else.
