Add a push mechanism in addition to the poll mechanism for variables

I've been thinking about how we do variables and I think a hook is a horrible idea. Or at least an incomplete one.

In general...a module serving up a specific page looks like this:

foo_menu() {
  // Menu declaration pointing to foo_page() as the callback.
}

foo_page() {
  // Do some stuff.
  // This knows the context it's on, because it defines it.
  // Do more stuff.
  return $stuff;
}

foo_omniture_variables() {
  // This has to try to determine the context with menu_get_object or arg() or get_context().
  // And then build up the variables with data that was probably available in foo_page()
  // And ultimateley, return stuff.
}

It would be so much easier if foo_page() could call something like omniture_set_variables($variables) and omniture would just store those up in a static or a session variable and ultimately they would get spit out.