Checkbox Field

Example:

<?php
class Checkbox_Fields_Widget extends WP_Widget {
    function __construct() {
       // Instantiate the parent object
       $widget_ops = array(
            'classname' => 'widget_checkbox_fields_entries',
            'description' => esc_attr__('Checkbox Field Widget - Created by deshisoft', 'eye-theme')
        );
        $control_ops = array(
            'width' => 275
        );
        parent::__construct( false, 'Checkbox Field Widget', $widget_ops, $control_ops );
    }
    function widget( $args, $instance ) {
        extract( $args );
        // Widget output
        $title = apply_filters('widget_title', $instance['title']);
        $checkbox = apply_filters('widget_checkbox', $instance['checkbox']);
        echo $before_widget;
            echo '<div style="border:1px solid #ddd; background:#f6f6f6;padding:15px;">';
               echo esc_attr($title);
               echo esc_attr($checkbox);
            echo '</div>';
        echo $after_widget;
    }
    function update( $new_instance, $old_instance ) {
        // Save widget options
        $instance = array();
        $instance = $old_instance;
        $instance['title'] = strip_tags( $new_instance['title'] );
        $instance['checkbox'] = strip_tags( $new_instance['checkbox'] );
        return $instance;
    }
    function form( $instance ) {
        // Output admin widget options form
        $title = $instance['title'];
        $checkbox = $instance['checkbox']; ?>
        <p><label for="<?php echo $this->get_field_id('title'); ?>"><?php _e('Title:'); ?></label>
        <input class="widefat" id="<?php echo $this->get_field_id('title'); ?>" name="<?php echo $this->get_field_name('title'); ?>" type="text" value="<?php echo $title; ?>" /></p>
        <?php _e('Checkbox : '); ?>
        <p><input type="checkbox" name="<?php echo $this->get_field_name('checkbox'); ?>" value="1" <?php checked('1', $checkbox); ?> />
        <label>Yes</label></p>
       <?php
    }
}
function checkbox_field_register_widgets() {
register_widget( 'Checkbox_Fields_Widget' );
}
add_action( 'widgets_init', 'checkbox_field_register_widgets' );
?>

Theme Folder -> function.php
Add this line:

require get_template_directory() . '/inc/checkbox_widget.php';   // inc folder name depend on your theme.

Download Checkbox Widget Field