An elderly person I know has recently had a stroke and will shortly
return home. Mentioned as a good idea was a method to isolate the
gas cooker if she is left alone for a while - reason being in case she
forgets to turn it off - and to get in touch with a Corgi registered
plumber to do the job. Anyone any idea of such a device and just what
it does? Never heard of the like myself, so wondering as to what it
is and the likely cost.

TIA