Context Condition (.module file)

MYMODULE.module

<?php
/**
 * @file
 * Module for defining custom context condition
 */
 
/**
 * Implements hook_context_plugins().
 */
function MYMODULE_context_plugins() {
  $plugins = array();
  $plugins['MYPLUGIN'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'MYMODULE'),
      'file' => 'MYPLUGIN.inc',
      'class' => 'MYPLUGIN',
      'parent' => 'context_condition',
    ),
  );
  return $plugins;
}

/**
 * Implements hook_context_registry().
 */
function MYMODULE_context_registry() {
  return array(
    'conditions' => array(
      'PLUGIN' => array(
        'title' => t('TITLE IN CONTEXT CONDITIONS ADMIN UI'),
        'description' => t('DESCRIPTION IN CONTEXT CONDITIONS ADMIN UI'),
        'plugin' => 'MYPLUGIN',
      ),
    ),
  );
}
/**
 * Implements hook_init().
 */
function MYMODULE_init() {
  if ($plugin = context_get_plugin('condition', 'MYMODULE')) {
    $plugin->execute($key);
  }
}

MYPLUGIN.inc.php

<?php
/**
 * @file
 * Extend context condition
 */

class MYPLUGIN extends context_condition {
  /**
   * Condition values (example from sitewide context).
   */
  function condition_values() {
    return array(1 => t('Always active'));
  }
  
  /**
   * Condition form (example from sitewide context).
   */
  function editor_form($context = NULL) {
    $form = parent::editor_form($context);
    $form[1]['#title'] = t('Always active');
    $form['#weight'] = -10;
    return $form;
  }
  /**
   * Condition execution.
   */
  function execute($value) {
    foreach ($this->get_contexts($value) as $context) {
      $this->condition_met($context, $value);
    }
  }
}