Fatal Error Notify
This plugin sends you an email notification whenever a fatal error (or other error level, configurably) is detected on your site.
Unlike traditional uptime monitoring services, which will only notify you if your entire site is down, this plugin can notify you when an error is detected on any page or process on your site.
Automatic plugin and theme updates often introduce problems that you aren’t aware of until they’re reported by your visitors. Fatal Error Notify lets you address these issues as they occur and before they cause significant problems.