When a smoke alarm goes off, it’s telling you to get out of the house. The Nest design encourages opening an app on your iPhone instead. A smartphone has many uses but it is not a practical fire extinguisher.
Each of its convenience features for non-critical events is potentially a deadly distraction when life is a matter of seconds. It’s the smoke that usually kills.
Not to mention that these alarms do both types of smoke/fire and carbon monoxide all in one.