I wanted to add custom Input Checkbox Type in product custom option and I have followed bellow link in order to add the type. This is working fine as default value (always associated/added to the grand total if it is checked or not) not as an optional, like checkboxes behavior.
Tutorial link - http://magento.ikantam.com/qa/custom-input-types-custom-options
Makes it possible to add another custom input type "checkbox" or not?
If yes, then where I will have to make changes in order to work like checkbox?