When they released the Nest Protect fire and carbon monoxide detector last year, I admired the way they had looked at the common usability irritants of existing detectors, such as the chirping and the nuisance alarms, and they solved them in a way which was safer for everyone. The price tag of $129 seemed a bit high but hey, they are functional and beautiful.
As Consumer Reports themselves said: “It would have been a real game-changer if the Nest Protect contained all three sensors (one for CO, and the two for fire), something we’ve been calling on manufacturers to develop.”
Judging from the Kidde’s price tag, adding another sensor would not have added much to the cost of the Nest Protect and it would have provided the best protection.
My product wisdom from all of this: always consider usability, have great features and functionality, always strive for great design, but don’t forget the basics. Define what it is your product has to do and make sure it does it.