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.

This is yet another search solution for things you may lose within you own four walls - but with a new twist. Remember those key pendandts that made sound when you whistle? Something like that for finding small objects like phone or remotes. There would be one base unit (appliance). You could change frequency on it (135, 136,137 ...) with simple + - buttons. When click on send it would transmit that frequency in small area. Enough for house or flat. Each small object would come...

At 8 am someone is ringing at your door, for half an hour. Enough to wake you up, but not enough for you to get up. If only there was a button marked "Press here to leave message". After pressing it, the message would be videotaped (or audio recorded only in cheaper version). You could find out who it was and what he or she wanted. Based on a true story