How about a robot that hits the snooze button for you? xD
Ummmmm... I guess it sorta depends what you want to define as a 'robot'. I mean what level of complication and artificial intelligence are we talking?
Simple things like putting the toilet seat down, making sure the shower curtain is always closed, drying the floor after you've gotten out of the shower would all be pretty useful assuming they were kept discrete and out of the way.
Maybe some sort of system that would 'know' when you've left the house for a certain period of time and would make sure all your lights, stove, sinks, etc were turned off?
Personally, for household use, I think discrete is probably the best option for most ideas. The home is cluttered enough with appliances as is.