This wonderful example of how to practice creatively by classical musician and composer Nahre Sol works well for singers. Adding a phrase or pattern of your own to a section of song you're working on takes away the sense of grunt work and repetition. I will add that this type of practicing helps the singer enter an alpha state which encourages focus, interestingly and almost counterintuitively.
Looking at your cell phone or watching the ballgame isn't the same thing. This method immerses you in your practice and improves your singing or playing more efficiently. Watch her video here.