Robot vacuum cleaner. Programmed to switch itself on at the same time every day and pootle around sucking up crap. All I need to do is remember to empty the dust compartment a couple of times a week, and wash the filters once a month.
Robot floor cleaner. I call it the work house orphan (channelling Agatha Christie and Miss Marples' many housemaids) because it has a setting option that mimics a person on their hands and knees crawling along and wiping the floor, though it's real name is the Moneual RS700. Similar to the aircraft powerglide hard floor cleaner mentioned upthread in that it has two rotating disks that do all the work, but once I push the start button it bimbles off across the floor without any further input from me, so I can sit here mumsnetting while it slaves away on my behalf. It is slightly more demanding than the vacuum, because the water reservoirs need to be filled, and the microfibre pads rinsed and attached before use. It does have a remote control, but can't be programmed to come on automatically when I'm not home. Once started it runs for 40 minutes, and leaves the bathroom, kitchen, living room and hall floors spotless.
Another vote for the Instant pot, as a vegetarian I eat loads of beans and pulses, so it paid for itself quite quickly due to the difference in price between tinned beans and dried beans. Love being able to leave it to get on with the cooking while I go out and potter in the garden.
Halogen oven, very useful for baking and grilling single portions without having to heat up the big oven.
Counter top dishwasher that I can load and unload without having to bend down (on account of being doddery).
Sometimes I sit here mumsnetting, with the washing machine, dishwasher, floor robot and instant pot all slaving away in the background and think how lucky I am compared to the women who lived on this street a hundred years ago. They had to fetch water from the street pump, heat it on the range, and then rub their weekly wash by hand against a washboard, using lye soap that cracked their skin. Washing nappies, snotty handkerchiefs and sanitary towels. Having to walk to the shops every day because they didn't have fridges. Having to clean grates and start fires every morning, waiting for kettles to heat over ranges. Heating bathwater in pans on the range. AND with all that to do they even made extra work for themselves by competitively donkey stoning their front steps. I wonder what they'd think of the constant hot water from the gas combi boiler, and the power shower, as well as all the other devices.
Since getting the floor cleaning robots my floors are always clean. I just wish someone would hurry up and invent a dusting robot, because the contrast between the shiny floors and layer of dust that accumulates on all the other horizontal surfaces is a bit depressing.