I think a panic button for older adults is a terrific idea. One in the bathroom, one near the person's bed and maybe one she carries around or wears on a pendant.
For mobility-limited people, how about a door opener like the grocery store has? When I step on to the pad, the door swings open.
Program every clock in the house to the same time (daylight saving time or after power outages).
Cut power to my iron after a few minutes if I forget to unplug it.
Turn on not only the porch light, but a lamp inside the house as well (so I don't walk into a dark house).
Smart smoke and carbon monoxide detection systems. A thermostat that adjusts the heat and humidity in the house automatically.