Can I use a walkie-talkie app to send audio from 1 iOS device to another?
There are a bunch of wifi walkie-talkie apps in the app store. Would it work if I got 1, hook something like a cd player or mp3 player up to an iOS device through the headset jack or lightining connecter, then send the audio to a second iOS device on the same network if both iOS devices were running the same app?
What would be the purpose of this? There is the possibility of simply sending audio files recorded with the voice recorder to your own iMessage account then you can simply open it on the other device, or are you asking for something that will automatically play the sent data once the audio has been sent?
In theory, yes, if you've got a way of getting audio onto your phone like it is a mic, that will come up in the walky-talky app on the other device, I don't ink that the headphone jack quite works in that way as an input though, I know there is a mic on the apple ear buds but I think it is a specific protocol.
The results would likely not be impressive. Assuming you could get audio in the headphone output or lightning connector, and then found a way to route it to the walkie talkie app, the sound received won't be great to listen to. These apps use bandwidth saving compression and frequency filtering to minimize data usage.
While some tout HD quality sound, I think you'd find it wouldn't sound much better than if you made a regular phone connection and put one device up to a speaker, and the other to your ear.