Good introduction video.


Product page also indicates the units all link together wirelessly on their own over 802.15.4. No need for working WiFi to still have the multi room notifications. WiFi is for setup, and for the mobile notifications integration.

Nest Protect for Security Systems is coming in 2014 (Integrates with other security systems). http://support.nest.com/article/What-is-Nest-Protect-for-Security-Systems