A simple example of creating a custom select element, using the FormElementManager to handle the external dependencies.

CustomSelectElementWithFormElementManager.php

<?php
/**
 * Define the custom form element
 */
namespace Forecaster\Form\Element;

use Zend\Form\Element\Select;
use Zend\InputFilter\InputProviderInterface;
use Zend\Validator\Db\RecordExists;
use Zend\ServiceManager\ServiceLocatorAwareInterface;
use Zend\ServiceManager\ServiceLocatorInterface;

class ArticleList extends Select implements InputProviderInterface, ServiceLocatorAwareInterface
{
    protected $validator;

    protected $serviceLocator;

    public function setServiceLocator(ServiceLocatorInterface $sl)
    {
        $this->serviceLocator = $sl;
    }

    public function getServiceLocator()
    {
        return $this->serviceLocator;
    }

    public function init()
    {
        $validator = new RecordExists(array(
            'table'   => 'articles',
            'field'   => 'id',
            'adapter' => $this->serviceLocator->getServiceLocator()->get('Zend\Db\Adapter\Adapter')
        ));
        $validator->setMessage('Please choose a valid article!', RecordExists::ERROR_NO_RECORD_FOUND);
        $articleTable = $this->serviceLocator->getServiceLocator()->get('Forecaster\Table\ArticleTable');
        $this->setValueOptions(array_merge(array(-1 => 'Please Choose'), $articleTable->getSelectData());
        $this->validator = $validator;
    }

    /**
     * Get a validator if none has been set.
     *
     * @return ValidatorInterface
     */
    public function getValidator()
    {
        return $this->validator;
    }

    /**
     * Sets the validator to use for this element
     *
     * @param  ValidatorInterface $validator
     * @return \Forecaster\Form\Element\UserList
     */
    public function setValidator(ValidatorInterface $validator)
    {
        $this->validator = $validator;
        return $this;
    }

    /**
     * Provide default input rules for this element
     *
     * Attaches a phone number validator.
     *
     * @return array
     */
    public function getInputSpecification()
    {
        return array(
            'name' => $this->getName(),
            'required' => true,
            'filters' => array(
                array('name' => 'Zend\Filter\Int'),
            ),
            'validators' => array(
                $this->getValidator(),
            ),
        );
    }
}

?>

<?php
/**
 * Define the form, which will use the element
 */
namespace Forecaster\Form;

use Zend\Form\Form;
use Zend\ServiceManager\ServiceLocatorAwareInterface;
use Zend\ServiceManager\ServiceLocatorInterface;
use Forecaster\InputFilter\ArticleInputFilter;

class AddRecordForm extends Form implements ServiceLocatorAwareInterface
{
    protected $serviceLocator;

    public function init()
    {
        $this->add(array(
            'name' => 'articleList',
            'type' => 'ArticleList',
            'options' => array(
                'label' => 'Articles'
            )
        ));
    }

    public function setServiceLocator(ServiceLocatorInterface $sl)
    {
        $this->serviceLocator = $sl;
    }

    public function getServiceLocator()
    {
        return $this->serviceLocator;
    }

    public function __construct()
    {
        parent::__construct('AddArticle');

        $this->setAttribute('method', 'post')
            ->setAttribute('action', '/forecaster/admin/articles/add')
            ->setAttribute('class', 'form-horizontal');

        $this->add(array(
            'name' => 'submit',
            'type' => 'Zend\Form\Element\Submit',
            'attributes' => array(
                'class' => 'btn btn-primary',
                'tabindex' => 1,
            )
        ));

        $this->get('submit')->setValue('Add');
    }
}

?>

<?php
/**
 * Define the action retrieving the form via the FormElementManager
 */
namespace Forecaster\Controller;

use Zend\Mvc\Controller\AbstractActionController;
use Zend\View\Model\ViewModel;

class AdminController extends AbstractActionController
{
    public function addArticleAction()
    {
        $formManager = $this->serviceLocator->get('FormElementManager');
        $form = $formManager->get('Forecaster\Form\AddRecordForm');

        if ($this->getRequest()->isPost()) {
            $form->setData($this->getRequest()->getPost());
            if ($form->isValid()) {
              // ... do something if it's valid
            }
        }

        return new ViewModel(array(
            'form' => $form
        ));
    }
}
?>

<?php
/**
 * Define the getFormElementConfig method in Module, specifying the custom form element
 */
namespace Forecaster;

use Zend\ModuleManager\Feature\FormElementProviderInterface;

class Module implements FormElementProviderInterface
{
    // ... 
    public function getFormElementConfig()
    {
        return array(
            'invokables' => array(
                'ArticleList' => 'Forecaster\Form\Element\ArticleList'
            )
        );
    }
}
?>