kind of stupid, because people aren't apt to be careful or alert when they're walking because there's not much real danger. i'm sure the results would be the same as if these kids put on some headphones and listened to music while they walked... but if they listen to music and drove they'd still be fully capable drivers.
that's not to say there's no danger whatsoever to talking on the phone while driving, but this is a stupid way to try to prove it.