Consider: Take away the computer after school. Change the wifi password. Take away the power cord. Put the iPhone in a lockbox. Controlling variables outside the house is difficult but there are some alternatives in your own home. Perhaps it's hard to get things back under control; don't be afraid to enlist the help of a professional.
Here are two articles by Dr. Brent Conrad with more information: Children Addicted to Computer Games - Top Ten Tips for Parents and Child Video Game Addiction - Facts & Solutions.'