My 8 year old loves to play video games (who doesn't right?) but before she allowed to play she has to read for the amount of time she wants to play for the day. Her game time is cut off at an hour each day. That way if she wants to play for an hour she has to read for an hour first.
I have a list of at-home exercises that I know I can do. Whenever I play a video game, either at a save point (if the game has it), or at any "break" in the game, I step away from the console, choose an exercise on the list, and do a full set before I return to playing.