Right, I have a specific app need which I think should be possible *on paper* but I've no idea if it's ever been implemented:
I need, basically, a walkie-talkie; speak in one device, and it comes out of the other. But there's one crucial caveat: I want it to do so *only* using direct device-to-device networking, not being dependent on mobile internet or being connected to a common wifi hub.
And, just for good measure, being cross-platform between iOS and Android would be good, because while I might have an Android, I'm not entirely sure what the recieving handset would be.
If speech is asking too much, text might be viable.
(The ultimate goal: the ability to communicate between two cars on a long journey in a place where roaming is expensive)