I think the combination of the photoelectric smoke sensor and the heat and humidity sensors within the same device is a great idea. We have all had false alarms where the alarm goes off simply because it detects smoke even where there isn't any fire. Adding in the heat sensor should tell the device whether the smoke is cause by a fire or not.
Many of the great comments here are answered by a quick read of the Nest website (audible alert, nightlight, battery warning, etc).
BTW, an audible low battery warning is legally required for all smoke/CO detectors sold in the US and presumably everywhere else.
The suggested "features" are interesting...but keep in mind that safety-critical products have to ensure that the basic function works (or detects a failure) despite failure of components, user mistakes, or intentional tampering. Software QA is extremely rigorous so adding "features" adds to the analysis task. (Mute-by-time requires a clock...what if the time is wrong...even setting PM vs. AM could be disasterous! How would the unit detect this? How can consumers who can't be relied upon to renew the batteries be trusted to set and monitor the clock and change the time in the spring and fall?)
This detector is certainly a major step in both performance and complexity. Most of the consumer grade detectors appear to be designed with a goal of an absolute minimum of components and general expense. This one is orders of magnitude more complex.
While I don't see much reason for including a night-light function, I really like the amr-waving motion dtector for activating the temporary switch off. As a note, an automated switch off based on anything would be extremely unsafe, since it would have no means of determining that a particular activation was not a real fire. Arm waving to fan smoke away is something that indicates a human decision has been made that the situation is not a fire in progress. So it is a very good add-on.
That coating of the electronics is probably intended mostly to protect the package from the conductive dirt film that builds up on some ceiling mounted detectors.
Ideally, this thing would have voice recognition, you could say "alarm mute" and it would silence for 20 minutes until the cooking smoke cleared. Or a smart phone app that would mute it for you at the touch of a button. A lot of people can't reach the device to silence or remove it without getting on a step stool. The arm waving thing seems silly...
I agree naperlou - just add some code. Maybe have two different frequencies for the alarm or a pulse versus a tone. They might need a HW mod like an additional chip for the battery level autodetect but I think it would be well worth it. I hate not knowing how close my smoke alarms are to not being effective.
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