switch
as a field type.
array(
'name' => __('Switch Field', 'cmb2'),
'id' => $prefix . 'switch_field_id',
'desc' => __('Switch Field Description.','cmb2'),
'type' => 'switch',
'default' => 0,
'label' => array('on'=> 'Yes', 'off'=> 'No') //default On, Off
)