I don't know of anything that wouldn't require some space, either for a box with a locking cover or motors that open and close valves.

Anything with ability to be controlled remotely will be expensive, so much so that you'll be better off with a new appliance. Induction might be good in this instance.

Safety devices exist that may be appropriate for your situation. One possible solution is to fabricate a locking metal cover that prevents access to the knobs if the configuration of your range allows it.

You may also consider something akin to this device.

I cannot recommend the above by the way, no experience with it, but it seems like it might be a good idea. It allows complete lockout by the caretaker with a password, etc., while allowing access for fully cognitive users.

Thanks guys,

Ive decided to go with a conventional ball valve "lock out device". I just dont know if I need to go through the wall into the garage and place the second valve there, or if I can raise the pipe up to within reach along the wall behind the stove and back down so it is accessible. I have to check if that is against code.
Thanks for your suggestions.

Here's what I did for my water heater flush valve. I took out the original multiturn valve and replaced it with a ball valve that has a simple handle held on by a single screw. I took the screw out and put the handle and screw in a plastic bag taped to the side of the water heater. This prevents kids (and adults) from accidentally opening the valve but still allows for easy access. Most ball valves have a simple handle like that so the "conventional ball valve" you mentioned probably has that already. Then the caretaker can just take the handle after turning off the gas and bring it back to turn it back on. It doesn't even need to be screwed back in to do a simple single turn so it's almost like a key. No need for any special "lock-out" device.

Good luck.

You may want to check if the range allows gas to flow when power is out. If your range does not flow when power is out, you may be able to install a switch for the range or even just throw the breaker if it is on it's own circuit. If you install a switch. A switch that operates with a key could be installed.

You should also check with a fireplace store. As an example the log starter in my fireplace has a key that goes into an opening in the floor. I think this is just an long stemmed valve. There are also some electrically operated valves for gas logs but these may also involve having an igniting system.

In terms of fire codes I think the main part of the code is that there be a valve adjacent to the flex line. I'm not sure if there is something against having an extra valve in the line. You definitely should check with a plumber with this question.

Pull the knobs off when not in use.

You might contact your local Alzheimer Association. They often face these questions, and usually have good suggestions that anticipate long-term consequences from progression of the disease. Also, if you tell the Association of your experience with whatever approach you take, they can spread that knowledge to help others. Good luck.

Ok so if removing the knob is too easy, you could hire a plumber to install one of those gas values often used for gas fireplaces. They have a key that you insert and turn to open/close the valve.

Here is a link that might be useful: something like this..