WPEnforcer monitors the uptime for your website, and send you a notification when the website stops responding. You can configure to receive email as a notification.
An amazing feature It have is the capability to block entire countries from submitting the data to your website, while still allowing them to visit your website, for example not allowing them to post a comment or submit a contact form.
Another great features is that it checks the ip of the person submitting or trying to interact with the database with the huge list of blacklisted ip names.
Give it a try, they do offer a free version.