The Oven Timer Strategy is a great solution for putting an end to manipulation.  "Start engaging in problem solving or you will lose a minute toward your allotted time with your iPhone."  For more, see You Are Your Child's Best Psychologist.  

The use of this strategy is great for bed time ritual, homework problems (i.e. procrastination), video game limits (or lack thereof).

See Dr. Dan’s new book: https://www.amazon.com/dp/1935576062/?tag=medrounpublic-20