Nest released their Nest protect. Looks pretty awesome! http://nest.com/smoke-co-alarm/life-with-nest-protect/
gulp $130 / each. I need four. Also awaiting tech specs (assuming Zigbee) and to see if they allow it to be “open” - or if they use some proprietary shenanigans to lock it down. From their press release about an open API next year, I’m thinking it’ll probably be pretty open, though.
I have 4 detectors in my place - do I get two Nest detectors - or, for slightly less money, get the First Alert Z-LINK that will talk to SmartThings and cover all my detectors? Also not seeing a Z-LINK hardwire option, so I may opt for “neither” and see where things are in a few months.
…and it looks like it uses Wifi, not Zigbee, using the Nest thermostat as a proxy (as I had assumed it would). Pretty interesting - that could explain some of the cost. Wonder how battery life is for something like that?
I also wonder if they’ll release a reduced cost non-Wifi version down the road?
Also - it does not use the interconnect wire, which is a deal breaker for me.
The lack of the interconnect wire for me is a deal breaker for me as well. This is a strange omission from the AC version, since I would be willing to bet that any house wired to accept AC smoke alarms is also wired to interconnect them.
This is my near perfect vision for a smoke alarm/sensor combo though. The cost is a little higher than I expected. I have 7 smoke/CO2 alarms so I would be looking at $900+tax to completely switch. In 6 years when I have to replace my existing smoke alarms, perhaps I will see what Nest Protect 5.0 looks like 
What’s the interconnect wire do?
I think the product looks great even my mrs was impressed, but I worry that smoke detectors generally only last 5 years or so ? What’s the life span on this in terms of it being an effective smoke detector?
The interconnect wire allows standard smoke alarms to communicate with each other (i.e. one goes off they all go off). Whether the power is on or off, they can still talk to each other over the wire.
The Nest Protect seems to use two wireless protocols to communicate with each other: standard Wifi and then a secondary mesh network if power down (and therefore probably no wifi available). I still think the interconnect wire would have been much easier to implement.
I am curious about the longevity of the Nest’s as well. Some municipalities require you to change the smoke alarms every 7-10 years.