I will admit it's been some time since I've been within the marketplace for a smoke detector. A cursory scan of Amazon, however, signifies an average worth between $10 and $30, with combo smoke/carbon monoxide detectors landing at the upper end of that spectrum. In either case, it is a variety the $99 Protect misses by a rustic mile. In fact, this is not simply any smoke detector. Like the educational Thermostat before it, it's a little bit of house electronics aimed at gadget nerds, and certainly Nest has managed to do quite a bit in an in any other case staid class.