as a part of managing all the application's https certificate in a huge data center , i created it for the said purpose.
this script can be scheuled in cron or any batch scheduler , which output as a html page and can send a mail to defined mail address with the list of website/application name and the expiry date of the https certificate.
you can give a number of your sitesname name you want to monitor in the parameter file.
It is easier and you can anticipate for https certificate [url removed, login to view] cause no damage to your ssl applciation.
I used it ,beacuse i faced problems many time that our ssl certificate gets expired and our sigle signon stopped working, which cause ITP (interrupt to production).