How to use two Android smartphones as lavalier microphone transmitter and receiver? I have two Android smartphones (Nexus 5 and Galaxy Nexus) and lavalier microphone. I would like to connect microphone to one smartphone and connect another smartphone to the mixer console. Then stream audio from lavalier microphone to the mixer console directly via one smartphone to another over Wi-Fi or Bluetooth. Maybe router should be added to this network, to expand the range.

I work on stage in noncommercial events, so buying real transmitter and receiver will be to expensive for me, or for organization.

Theoretically it can be done through simple call, but there will be latency (it is not direct connection) and it will cost money every time..

I found several similar questions here, but no one was about using one smartphone with microphone, and I didn't found any answer yet.
I've come up with what is hopefully a better solution. Use the app here. Install the app on both devices. There are many similar apps to this so if this one doesn't work perhaps try another one. The app listed works over Bluetooth rather than WiFi. I hope this is OK and it should avoid latency. I'm not sure why I didn't make the link in my head that what you needed was a voice communication app. The old solution is below:

There certainly seems to be a gap in the market here because I can't see why this would be impossible (actually, thinking about it, capturing all device audio might be an issue [although you would only need to capture audio input which wouldn't be...]). I have a solution but it's a rather hacky one and will require root, I'm afraid.

NOTE: I haven't used any of these apps myself. Be careful when installing unknown applications.

Host a WiFi hotspot on one device and join the hotspot on the other. Make sure to turn off data before doing this. This way, the devices won't have an Internet connection but they will have a network connection.

Install AirAudio on the device that you wish to stream from.

Install Microphone on the device that you wish to stream from (this app may have some latency but hopefully not).

Install UPnPlay on the device that you wish to stream to.

Turn on the Microphone application so it starts recording everything and then set AirAudio to stream all device audio over DLNA and then use UPnPlay on the other device to recieve this stream.

I don't think this will work well in practice but it may be worth a try.

Hope this solves your issue.