How do I, an lone app vendor, verify that my call makes it out of the phone, or abort it without 911 noticing a dropped call? The radio+network part is a black box from my perspective
PS: At least where I live, emergency services will show up at your house if you make a few 0-second 911 calls
You can contact your 911 call center through a non emergency line (numbers available here when you enter your state/region: https://www.nasna911.org/contact-911). You can then call and set up a time window for outbound test calls to be placed where they won’t send emergency services.
I've worked on some custom Android firmwares before, and I did this for our releases. It's easy, the 911 call center doesn't mind (it's scheduled beforehand), and it ensures that the phone can dial 911. If you can't manage to test emergency calls, don't release phone software.
Yes, that's the clear and obvious answer. We have regulations around things like being able to make 911 calls for a reason, because it's literally a life and death issue. Nobody should be making or selling a call-hijacking app if they can't perform even the most basic level of testing to ensure 911 calls still work.
You call the PSAP's non-emergency number and ask to schedule a few test calls. If you don't know how to reach them, call your local police non-emergency number, they'll be able to put you in touch.
You're supposed to do this when setting up new VOIP service too, to make sure location information is reported correctly. It's quite a normal thing and they're not at all surprised by it.
I would go so far as to say there are 2 types of phone people: Those who've placed a lot of 911 test calls, and those who're placing their users at risk.
PS: At least where I live, emergency services will show up at your house if you make a few 0-second 911 calls