In my view, the more channels of notification the better. Our tool "
3CX Emergency Notifier" provides notifications by phone (IP phone, web client, overhead paging, IP speakers), email, SMS, and desktop popup.

If this was an actual emergency, all the details about precisely who dialed the emergency number, and where the person is, would display. An (optional) audible alarm would sound along with a text-to-speech message.
With our tool you can specify precisely where the person is located -- address, building, floor, section, and room. Alert information is based on templates that can include instructions regarding the steps the front desk should take, etc.
We also offer panic buttons and alarms (BLF on phone), along with very precise control over who is notified based on the location of the caller.