This tool has actually been posted for some time now but I failed to highlight it in my blog…until now.
There are a few other blog articles out there that detail the functionality provided by this new add-in, but to some it up, the data portion of the add-in is powered by a custom timer job that periodically gathers information about certain aspects of the farm and keeps a dedicated SharePoint list updated with the latest status. The second half of this solution is an add-in to Visio that connects to this dedicated list and generates/updates a diagram based on the information stored in this list.
Here are some of the other write-ups on this tool
Here is the add-in on codeplex
Here is the timer job on codeplex
Keep in mind that this timer job alone creates this list, gathers that data and keeps it up to date. This data could be used by a number of different applications other than Visio, but remember, you can connect the shapes in any Visio diagram to data hosted in a SharePoint list, so use the diagram that our add-in generates or BYOD (Bring Your Own Diagram).
Here is the sample diagram that was created using this solution add-in with some customizations