I carry mine all the time, for several things. First, obviously for safety. When hunting with my wife and/or son, we keep each other updated as to how things are going, seeing or not seeing deer etc.
I used to ring book along for long sits on stand, and hated the movement of turning pages etc. Now I download a book and can read, I always have the camera for pics/video, and was ale to watch my Tigers playoff baseball. Typically I just use it to read a book, or check in with each other. I dont answer calls. It can also double as a low level flashlight walking in after dark if I just need a short bit of light to navigate around something etc.
Now if they just made one with a built in gutting knife, drag strap and broadhead sharpener, I could just about ditch my fanny pack all together.