Well they don’t work across all medias.
You cannot issue requests through the XMLHttpRequest to other domains or subdomains. If you are issuing the request from www.foo.com you also need to target the request at www.foo.com and make certain to remember the www.
If you really need to hit another domain you can use JsonP where the browser utilizes the <script> tags ability to load scripts from a different domain. The loaded script then executes a callback function to give you the data. But for regular AJAX calls you cannot leave the source domain at all.
Some alternative error/message handlers include: Loggly, Papertrail, Log Entries, or better yet create your own with Whoops which later I’d like to research and develop upon for my own error catching application.