[Tacopuck]

I have a nest smoke detector, its quite nice actually. Before the alarm goes off it gives you a 'heads up' that smoke levels are rising.

More importantly it gives these warnings alarm in a speaking voice AND as an alert on your phone. If you are at work say and a fire starts in your home, you will know (assuming the fire doesn't knock out the internet connection before the smoke detector detects anything - which i see as very unlikley)