Many of our customer in Health Sector have need for Duress/Emergency in their rooms, but this feature could also apply to old age homes and educational institutions.
Previous PBX phone systems often accomplish this by allocating one line button which has registration on each phone to a specific alert extension, for example "666". If anyone presses this button (or dials 666), all phones will ring showing the caller id on the screen (identifying the source) and if a specific ring tone is associated with that Account in the phone it is also possible to have a custom ringtone for the alert (in this case person hearing and viewing details on phone means they can respond immediately to the emergency, without needing to even answer the call)
I don't believe this possible in the current build since there is a maximum of 5 SIP forking allowed per extension. If there was a special feature code which can only allow more than 5 SIP forking for this specific purpose it may be achieved using this method above.
Paging might also be a method, but this relies on the person in distress being able to speak- so not really an alternative for such emergency.
The feature request would be very useful to leverage off Akuvox Big Button phones which have a dedicated SOS button.