UrlCheck is little script that verifies if a site has changed since last check.
You can setup a MailGun account to send emails. Please refer to https://www.mailgun.com/
./urlcheck.py http://wwww.google.com/
To enable periodic checks, please add it as a crontab task, this example will check http://camas.sedelectronica.es/board every day at 9:00 am:
0 9 * * * /home/pi/urlcheck.py http://camas.sedelectronica.es/board
This script is based on the md5 checksum of the site content. Some sites generate random id's each time the document is requested, please refer to the line that states '# Add custom filters here' to filter the content in order to get reliable results.