This originally was based on slider field

I've changed its structure to avoid loading of heavy jquery UI so its only used the basic HTML5 type range input

1. php Filter

function cmb2_render_range( $field, $field_escaped_value, $field_object_id, $field_object_type, $field_type_object ){

  $slider = $field_type_object->input( array(
    'type'  => 'range',
    'class' => 'cmb2-range',
    'start' => absint( $field_escaped_value ),
    'min'   => $field->min(),
    'step'  => $field->step(),
    'max'   => $field->max(),
    'desc'  => '',
	) );

	$slider .= '<span class="range-text">' . $field->value_label() . ' <span class="range-value"></span></span>';
	$slider .= $field_type_object->_desc(true);
	echo $slider;
}
add_filter( 'cmb2_render_range', 'cmb2_render_range', 10, 5 );

2. CSS

/* Range field */
.cmb2-range {
  width: 70%;
  float: left;
  opacity: 0.75;
  -webkit-transition: .2s;
  transition: opacity .2s;
}
.cmb2-range:hover {
  opacity: 1;
}
.range-text {
  display: inline-block;
  margin: 0 .5rem
}
@media screen and (max-width:782px) {
  .cmb2-range {
    width: 100%;
    float: none;
  }
  .range-text {
    margin: .5rem 0
  }
}

3. jQuery

// CMB2 range
$('.cmb2-range').each(function() {
    var span = $('.range-value');
    span.html('<strong>' + $(this).val() + '</strong>' );
    // Append the range value to each slider 
    $(this).on('input', function() {
      // update to the dynamic value
      span.html('<strong>' + $(this).val() + '</strong>' );
    });           
});