Is there a way to have a piklist checkbox field with only one choice that can be true or false based on whether it is checked?

I tried the following, but send_email isn’t given a value unless it’s checked, and I’d like to have it set the value to 0 when it is not checked.

piklist('field', array(
     'type' => 'checkbox',
     'field' => 'send_email',
     'label' => 'Send Email?',
     'value' => '1',
     'attributes' => array(
        'class' => 'text'
      ),
     'columns' => 6,
     'choices' => array(
       '1' => 'Enable'
     )
   )
)

In the past, I’ve used the workaround of having radio buttons, but I’d really like to just have an enable checkbox.

My workaround:

piklist('field', array(
     'type' => 'radio',
     'field' => 'send_email',
     'label' => 'Send Email?',
     'value' => 1,
     'list' => true,
     'columns' => 6,
     'choices' => array(
       1 => 'Enable',
       0 => 'Disable'
      )
   )
 )