Someone forgetful (can't remember who) has a habit of leaving the house with the gas stove or oven lit. I've been thinking of ways of detecting this, so that an alarm or something can trigger before that (er, nameless) person leaves....
Fitting some sort of gas flow detector on the cooker pipe sounds a bit tricky though, unless I go sort of industrial with ultrasonics. An alternative would be something that monitored the position of the hob/oven controls. A heat sensor would be no good - it would still be detecting warmth when the fire has been turned off.
Is there some gadget marketted already for this need?
Ideas?