Having a phone mounted on a bike is a must-have distraction tool for indoor biking. Watching videos on YouTube and Netflix movies have transformed my indoor biking into entertainment with suffering. Social media breaks, checking notifications, and sending texts are much easier to do when the phone is right in front of you.
While riding on Zwift, the phone also becomes an extension of the game. I use Zwift Companion App to keep an eye on my heart rate while giving "ride-ons" and chatting with other Zwifters.
Here is my current phone set up on an indoor triathlon bike: