Yes it's a fair point. It's just to test the theory at the moment and the Aqara sensor was handy to move easily from another use. Now I know motion sensors pick up on a gas flame I'll probably switch the Aqara for a Hue.
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Ok.. so a little bit of data from my first temp test
Temp sensor increased significantly within a minute of turning the burner on to low
(More than 5 degrees C)
Returning to ambient (as measured by multiple sensors in the kitchen and pretest readings) took approximately 10 minutes
One thing to note.. I didnāt leave the burner on for more than about 5 mins so I donāt know how hot it really got, this might affect cooling time.
Iām not sure how useful this is but there you have it.
Andy
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What about having the oven on? Will that cause a raise in temp as well? I only ask since having the oven on when not in the kitchen is not that uncommon.
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Hereās an ideaādoes your oven/stove use rotary dials to control heat flow?
The oven at my last apartment did, and I thought about how I could put small rare-earth magnets into/on the rotating knobs, and a contact sensor to detect when theyāre in the off position.
Anything thatās not in that spot means the oven/stove is on 
Another ideaāif your oven has a HOT light to indicate when either the oven itself or the stove is hot, you could put one of the small led identification sensors over that to get the same result.
Or, for those of us with electric stoves, use energy clamps over the wiring to measure current flow.
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Thanks for the test results. 
I think it is very useful. I've got a couple of temperature sensors on the way (you can never have too many!) and I will try out that method when they arrive. My motion sensor is working well but it's a bit vulnerable to spills or splashes being at hob level and having to be quite close to detect a low flame, so if I can hide a temp sensor under the extractor hood it might be a neater solution.
"Honey, why does dinner smell like melted plastic?" 
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Yes, that's my worry! 
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Update on this.
I am now using the temperature difference method for the gas hob being on rather than the motion sensor method. With a temperature sensor fixed to the underside of the extractor hood, it is out of sight and far enough away not to get cooked or get any splashes on, but it still picks up if a gas ring is on. I've found using a difference of anything greater than 2.5 Deg C from the room ambient works well. It detects even the smallest gas ring on the lowest setting within a couple of minutes and drops down below that within 5 or 10 minutes with everything off again.
For the electric oven, I have a new IotaWatt CT fitted to the Oven Supply at the fusebox and that can even detect if just an oven light has been left on, so that part is easy.
At the moment I just run the check rules at specific times just after periods when we might normally have the oven on and again if we turn the media system off which normally means we are about to go out or to bed. I'm sure it will evolve and as it stands it doesn't intervene, just gives a TTS warning message. There are also virtual switches for Hob and Oven active on the dashboard so I can double check if I want to when we are out, but given the checks above we shouldn't be able to leave the house with them on anyway unless deliberately.
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I really like this idea. It might be tricky to fit it in there of course. The recessed door sensors might have a chance of fitting inside the bigger knobs, but then you'd want to use a muuuuch weaker magnet. Or, if you could get underneath the metal stovetop panel you could place the magnet under the panel.
@Geoff_T Many thanks for the update. Although I don't know how I will be able to do alerts inteligently since we really have no schedules, I just may give this a try. Maybe better to err on the side of too many alerts with this one.
Yes it's helpful for me that there are only 2 of us and we have a reasonably predictable routine. If you are in a home with kids/shift workers etc etc it would be a lot more tricky to set up the test rules.
Have you thought about utilising a Peltier effect device
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What sensors did you get?
The existing room temperature readings are coming from a pair of Hue motion sensors, and I got another Aqara temperature/humidity sensor to stick on the extractor. I know people have had issues with the some Aqara gear but I have been using the exact same type elsewhere and they have been rock solid. I have many, many Tradfri outlets which I think helps.
I also figure if it falls of into the pasta it only cost Ā£10!
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Too bad pasta and the sensors are close to the same color.
I don't want to tackle Aqara sensors so I will need to try something else.
And taste the same if I'm cooking it.
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But they both turn out Al Dente.
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Could you point a camera at the control knobs . . . ?
@Geoff_T
This is really screaming out for a little app to control it all..
Not sure exactly what the triggers would be but Iāll have a think about it
(In between doing everything else )Ā§
Andy
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