Does anyone know if these play nice with other smoke detectors? I have 3 hardwired detectors in my house and I would like to replace one with a Nest detector. The other smoke detector trigger the alarms of all the others. Does the nest have that capability?
Also do we have Nest smoke detector integration for smartthings?
They won’t communicate with the other detectors. Each smoke detector brand communicates with their own brand, usually via a proprietary protocol. Nest uses WiFi to communicate in between Nest Protects, Thermostat and Cam, but it can’t use the orange wire that usually other brands use.
I believe there is a community device type for the smoke detector, but I don’t use it. You can search the community and find the discussion, though.
Thanks that seems short sighted of Nest. In a fire wifi could easily go down. If you have these in multiple rooms on different floors you would want one to notify the others that there is a fire.
Even if the other detectors if the battery goes out they still alert the others over that wire. 
I will have to look into something else.
Nest Protects makes their own secure Nest only WIFI network so they work together even is you lose your home WIFI.
Sorry about not being clear. They use their own WiFi network as @celblazer said. Here is more information on the subject if you want to read more about it:
This has been discussed on this forum at great length. The search icon in the upper right corner 
holds a wealth of community knowledge. I highly recommend using it first.
Here are some highlights:
https://community.smartthings.com/search?q=Nest%20protect
Nest protect is not for everyone but your concerns about wifi being unavailable during a fire and not being notified are only valid if you are not home. if you are home the alarm is VERY loud and obnoxious and unless you hearing impaired you will be notified. It is equally possible that your wifi stays up and your internet acces “goes up in smoke” and neither SmartThings or Nest protect can notify you remotely then.
I am thinking of a 3 story house with a basement. You have a fire in the basement I dont care how loud that thing is you won’t likely hear it in your sleep on the 2nd and 3rd floor. Have closed doors and it would be even worse. I’ll find a different detector.
Once it is set up, Wireless Interconnect will work even without Wi-Fi in your home, since it operates on a different wireless protocol to connect all of your Nest Protects.
That sounds promising but I’d have to buy 4 new detectors 
Thank’s hopefully they come out with something from the manufacturer I am already using.