ACM only shows errors for a single site. If you are managing a large ACM deployment this can be a pain because you may need to visit 10-20 web pages just to see if there are any errors in your ACM deployment.
This Sample web page shows an aggregation of all errors for all sites in a single view.
See the readme.txt file in the solution zip file for instructions on how to deploy this web page (the page would be deployed next to the other ACM web pages).
File AcmShowAllErrorsSamp.zip is attached to this blog post, it is a Visual Studio 2012 solution. Binaries are included so you do not need to compile.
This is a sample, no guarantees or warranty of any kind apply to it.
No security is applied, anyone who can access the web page will be able to see all of the error information. Whereas with ACM only a site administrator can see error information for the site.
Below is a screen shot of the sample error listing web page: