NDIntercom

This unique app turns your iPhone into a push to talk, and simultaneous receive intercom, using the NDI Protocol. Works on Wifi, Wired or 4G via VPN.
Using the industry standard NDI Protocol which is supported by hundreds of software and hardware devices, NDIntercom allows for audio monitoring of any NDI feed on your network for comms listen monitoring as well as talkback.
Simply launch the app and a new NDI service will be registered on your network with your PTT audio stream. You can lock down the PTT with the headphone button or a screen swipe. You can also switch to speakerphone and enter an NDI Discover Server address for cross subnet or VPN applications. You can also rename the device. Also supports Bluetooth headsets including Apple AirPods.
Has been tested with macOS Server VPN although other VPNs may also work. Requires a direct VPN connection (not relayed) for best results.
Use in pairs, or with a whole team monitoring a single director feeds, also compatible with Sienna ND Processing Engine Intercom server for party line operations. See website for compatibility details.
NB. NDIntercom provides a low latency audio connection using NDI uncompressed audio. Performance depends on quality of network connection, and may be affected by poor WIFI connections. Solid WIFI connections or a wired connection via lightning to ethernet are strongly recommended.