can you really possess the primary domain of the wordpress blog( to redirect to a different site and also the actual posts and pages (,, etc') not to be rerouted and rather reside around the wordpress?

add_action('init', 'redirect_home');
function redirect_home() {
  if( is_home() ) {

Which should get it done.

You could do this by using mod_rewrite:

RewriteEngine on
RewriteRule ^$ [L,R]

This situation is perfect for the .htaccess file within the document root directory and can redirect demands to

You might take a look at while using WordPress redirection function instead of the header location..

wp_redirect('someurl', 301);

301 may be the status code to make use of, not to mention someurl is how you'd place your Hyperlink to reirect to.. (301 is default, so not needed unless of course you'll need a difference status code)