Every house should have fire extinguisher around – just in case. So why leave it standing around without use. Here is a great idea about putting and alarm clock on it. Extinguisher balloon can serve as a great resonator for alarm. Especially CO2 type are great in resonating.
All you have to hang an Arduino based clock with relay based ringer. It’s OK to have it at home, but please, don’t take it outside – as it may look as a bomb to someone. Don’t limit yourself with alarm clock – it can serve as a general purpose even as a fire alarm wit proper electronics.