public function actionSendEmail()
{
    $criteria = craft()->elements->getCriteria(ElementType::Entry);
    $criteria->section = 'guide';
    $criteria->dateUpdated  > '("now"|date_modify("-7 days"))';
    $entries = $criteria->find();

    if ($entries) {

        $user_criteria = craft()->elements->getCriteria(ElementType::User);
        $user_criteria->groupId = '9';
        $users = $user_criteria->find();

        //Send to each User
        foreach ($users as $user) {
            //Send Mail
            $email = new EmailModel();
            $email->toEmail = $user->email;
            $email->subject = 'New Entry';
            $email->htmlBody    = '
            My HTML body goes here
            ';

            craft()->email->sendEmail($email);
        }
    }
}