Do I need a mobile phone/device to use the REVIAN RED system?

Yes.  You will not be able to start a treatment using the REVIAN cap without the REVIAN mobile app.

The REVIAN Cap is controlled by the free REVIAN app that must be downloaded from Google Play or the Apple App Store and installed on an Android or Apple (iOS) mobile device that has a camera, Wi-Fi or mobile network connectivity, a touchscreen, and Bluetooth. 

The REVIAN app is used to start and pause treatments, track progress, and set treatment reminders among other things.