1. Any iOS device which is running the VidiU app and sharing the mobile / cellular data as a network uplink for the VidiU should not be used for phone calls. Some cellular carriers do not allow simultaneous voice and data services and will stop the data connection flowing through the VidiU app; other carriers may reduce data throughput when a voice call is active.
2. It is recommended that iOS devices are placed in Do Not Disturb mode while providing a cellular data uplink for the VidiU to prevent any drops from that device. See Apple's article at this link.
3. The VidiU app must be running in the foreground on the iOS device when providing a cellular data uplink for the VidiU. If you press the home button on the iOS device or open another app, or if the device times out from the Auto-Lock setting or is manually placed on the Lock Screen, the uplink connection through that iOS device will time out and stop sending data.