tvOS UITableView cell focused

You must implement this delegate method:

- (void)tableView:(UITableView *)tableView didUpdateFocusInContext:(UITableViewFocusUpdateContext *)context withAnimationCoordinator:(UIFocusAnimationCoordinator *)coordinator
{
     //this gives you the indexpath of the focused cell
     NSIndexPath *nextIndexPath = [context nextFocusedIndexPath];
}

then you can do whatever you want with it in that function