You should be able to FaceTime 911 to give them a live feed (recorded on their end for evidence) of what's happening in case something happens to you or your phone.

If you're hiding and can't talk. If your in some kind of hostage situation. If you are sure you won't make it but want your assailant to be caught on tape anyway. Probably a bunch more reasons I'm not thinking of.. I feel like we have the technology to be making this a reality already.