seems awesome for recreational and emergency communication
In an emergency, using voice or CW will be heard by a lot more people, and understood by them a lot easier, more reliably, and better than having to have an app on both ends.
Don't get me wrong, it's cool tech (after I figured out what it actually is), but it should not be presented as useful in an emergency. In an actual emergency, the last thing that should be done is flaffing around with an app on the phone, and making sure someone on the other end happens to have the app installed as well.
Actually, EmComm, in many situations, is based on licenced software such as VARA running only on Windows with a bought key.
I think it's time to try open source software.
Your definition of emergency communication is way off. Sure you can use some app for training for that situation, however it's the least reliable way to get communications out in an actual emergency where others are actually going to hear and respond to it.
The best communications in an emergency, are those that are the most widely used. Which would be voice first, CW second. Having to carry around a phone, to use some app that someone else has to be actively listening to using another phone that is held up to a handheld, is not how I would want to be doing things in an actual emergency.
I also wouldn't rely on vara during an actual emergency. Sure a it's fun to play like using vara or a ht held up to a phone is going to help in any way during an emergency, but if you are relying on them, you are doing it wrong. I certainly wouldn't want my life to depend on them.
I've played around with this before, and it does indeed seem to work quite well via audio coupling, which makes me think it's probably a little more robust than typical packet. Glad to see the various new digital modes being developed for on FM. Some people just have an HT and need more toys to play with than just APRS.