Television appears to exercise attention, but I believe this is a facade.
Television: It might appear that television would be a great attention developer. Kids can sit and watch it for hours. But the lack of brain activity belies this facade.
The brain waves of a TV observer are more like the brain waves of someone who is asleep. Not a lot of neural development taking place there.
In addition, the rapid switching of brief scenes in many television cartoon shows works against the development of sustained focus.
There are a few exceptions which have merit. I highly recommend, for example, "Mr. Rogers' Neighborhood."
This show presents scenes that develop slowly (rather than switching every few second seconds like cartoons do). Here sustained focus is exercised and developed.