Long-time TYPO3 users are familiar with the messages displayed in the About > About Modules module, warning them of various wrong or undesirable settings. As of TYPO3 4.3, this information also appears as a global overview in the "Status Report" of the Reports module. Not only does that offer a synthetic view, but it is an improvement as it also shows what's right and not only what's wrong. What's more there's an easy API to add statuses (for example, Extbase adds a status which checks some eAccelerator settings).
The required system extension "sv" also adds a report by default. The "Installed Services" report displays all installed services, grouped by service type, along with their related information. It also shows whether a given service is available or not. At the bottom of this report is a list of all the paths that will be searched for executables, and whether each path exists or not.
There's also an API for creating new reports and adding them to the Reports module. There are not many yet, but Dan Osipov recently released an extension providing an overview of a memcache server as a report (extension key: memcached_reports).
Unfortunately the documentation is missing for now, but we hope to have it in 4.4. However if you look at the "reports" extension itself, or at the report provided by the "sv" extension, it should be quite easy to understand how a report is built and registered.
Thanks for the writeup! A small addition: Extbase adds a report as well, which checks if the PHP Accelerator (if you use one) is configured correctly, i.e. does not strip comments off.
Greets,
Sebastian