|dbojan (Bosnia and Herzegowina)|
Gas / propane / butane alarm
Gas / propane / butane alarm, that would measure amount of gas in the room. With sound/light alarm when it reaches critical values. Connected to phone line so it could call police after 1 minute (time to disengage fake alarms). Together with backup battery. Also, maybe a signal for emty battery, when there is no power grid.