What would happen in this scenario?
Smart things + ZWave Door Sensors + Fortress Z-wave siren + Sonos.
Internet is down and a burglar triggers the door sensor.
Is the siren going to turn on to deter the invader?
Is it possible to have a message played on the sonos without internet?
Is it possible to work around the issues without internet?
This is basically all i am missing for considering Smartthings as an excellent replacement for a regular alarm system.