A feature can be designed well, look attractive, fit into where it is located so that it does call any special attention to itself, and be fairly easy to figure out by the person getting ready to use it (whether they live in the home or are a visitor or guest), but it must require only the smallest amount of physical effort and exertion to engage or operate.
Not only is this a practical concept for people of all abilities, but as we age, we likely don't have the grip strength, hand flexibility, reach, stamina, coordination, or muscle mass that we add in earlier years. Thus, it makes sense to make things easier to operate for people as they age - whether it's a remote control, faucet, light switch, door handle, appliance, shower, or anything that we normally use around the house.
The operational force that we need to use - that required to engage an object and make it work as intended and designed - should become easier over time and not remain constant or even increase. Thus, as aging-in-place professionals, we need to make sure that we are designing and equipping the homes of our clients with controls, fixtures, switches, and other items that require only minimal effort to make them work correctly.
In terms of windows, the generally harder to operate single-hung or double-hung windows (especially for someone small or with limited range or motion or reach) can be replaced with easier to operate crank-out awning or casement windows - or even windows that can be pushed out or pulled open or even opened with a remote control.
Faucets - especially the single-lever ones - require less effort to operate than others, whether they are in the kitchen, the bathroom sink, laundry room, mud room, or tub or shower. Less effort translates to a safer and more comfortable experience each time also. In fact, some faucets can operate by sensing motion or just a light touch. The same is true for toilets.
Door handles can be real challenges for people - especially when the doors they are opening are large or heavy. Whether these are entry doors, doors into interior rooms, cabinet or pantry doors, or any found elsewhere in the home, they should not become a barrier to those living in or visiting the home. The doors might be installed for privacy, safety, security, or other reasons, but they need to open - the locks when they are present, the handles, and the physical doors themselves - as easily as possible without any particular effort. Anyone, regardless of their size, age, or ability, should have little to no difficulty in using them.
In addition, there are many other features, fixtures, and areas in the home that require someone to open them, turn them on or off, operate switches or controls, or otherwise use them. All of these need to be designed and installed with the expressed recognition that over time people have less effort to expend to use them.