FreePBX currently supports an "emergency caller ID feature." This feature allows admins to set a special caller ID for each extension, so that when that user calls a trunk designated as an emergency trunk, the emergency caller ID is sent.
This is a great feature, but there's one problem: When FreePBX is used in device and user mode, the emergency caller ID is linked to the USER and not the DEVICE.
This is important because the correct caller ID to send in an emergency should be determined by the location of the device and not by the particular user who is logged into that device.
For example, suppose that I have two homes. At both homes, I have a phone that is registered as user 200. The phone is at my home in California is device 300 and the phone at my home in New York is device 301. I use device and user mode so that any of my employees/users can dial 200 and reach me, wherever I happen to be, and I can get voicemails from either phone as well.
If I pick up the phone in New York and dial 911, I want the Emergency Caller ID to be a # that links to my New York location. If I pick up the phone in California and dial 911, I want my Caller ID to be a # that links to my California location. If the emergency caller ID were linked to the device, I could do that.
As it is now, however, Emergency Caller ID is linked to the user, i.e. user 200. So, everytime I go from one place to another, I have to manually change the emergency caller ID.
Honestly, I can't think of a reason why you'd ever want emergency caller ID tied to the user instead of the device. When dialing an emergency number, you almost always want the emergency services coming to the location of the device, without regard to the identity of the person using that device.